Symptoms of Swine Flu

Novel influenza A (Swine Flu) is a new flu virus of swine origin that was first detected in April, 2009. The virus is infecting people and is spreading from person-to-person, sparking a growing outbreak of illness in the United States. An increasing number of cases are being reported internationally as well.

It’s thought that novel influenza A (Swine Flu) flu spreads in the same way that regular seasonal influenza viruses spread; mainly through the coughs and sneezes of people who are sick with the virus.

It’s uncertain at this time how severe this swine flu outbreak will be in terms of illness and death compared with other influenza viruses. Because this is a new virus, most people will not have immunity to it, and illness may be more severe and widespread as a result. In addition, currently there is no vaccine to protect against this swine flu virus. CDC anticipates that there will be more cases, more hospitalizations and more deaths associated with this new virus in the coming days and weeks.

Novel influenza A (swine flu) activity is now being detected through CDC’s routine influenza surveillance systems and reported weekly in FluView. CDC tracks U.S. influenza activity through multiple systems across five categories. The fact that swine flu activity is now detected through seasonal surveillance systems is an indication that there are higher levels of influenza-like illness in the United States than is normal for this time of year. About half of all influenza viruses being detected are swine flu viruses.

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Since mid-April 2009, CDC, state and local health authorities in the United States, the World Health Organization (WHO), and health ministries in several countries have been responding to an outbreak of influenza caused by a novel influenza A (H1N1) virus (1). In March and early April 2009, Mexico experienced outbreaks of respiratory illness subsequently confirmed by CDC and Canada to be caused by the novel virus. The influenza strain identified in U.S. patients was genetically similar to viruses isolated from patients in Mexico (2). Since recognition of the novel influenza A (H1N1) virus in Mexico and the United States, as of May 6, a total of 21 additional countries had reported cases, with a total of 1,882 confirmed cases worldwide. Several WHO member states are conducting ongoing investigations of this worldwide outbreak, and WHO is monitoring and compiling surveillance data and case reports. On April 29, WHO raised the level of pandemic alert from phase 4 to phase 5, indicating that human-to-human spread of the virus had occurred in at least two countries in one WHO region. This report provides an update of the initial investigations and spread of novel influenza A (H1N1) virus worldwide.

Mexico

Since implementing enhanced surveillance on April 17, the number of suspected cases has increased rapidly, along with hospitalizations for severe acute respiratory illness (Figure 1). As of May 5, using an updated case definition of fever plus cough or sore throat for a suspected case and real-time reverse transcription–polymerase chain reaction (rRT-PCR) or viral culture for a laboratory-confirmed case, Mexico had identified 11,932 suspected cases and 949* cases of laboratory-confirmed novel influenza A (H1N1) virus infection, including 42 patients who died. Cases with laboratory-confirmed infection have been identified in 27 of 31 Mexican states and the Federal District. Confirmed cases in Mexico and in the United States have a similar age distribution (Table). Information is available on the clinical course of illness for 22 patients with laboratory-confirmed illness who were hospitalized, including seven patients who died. Five of the 15 surviving patients and one of the seven patients who died had underlying chronic medical conditions. Additional details on the clinical signs and symptoms of these and other patients are being collected. Among patients with confirmed cases for whom information was available, 56 (98%) of 57 reported fever, 49 (94%) of 52 reported cough, 23 (79%) of 29 reported dyspnea, 35 (80%) of 44 reported headache, and 34 of (83%) 41 reported rhinorrhea. The government of Mexico has instituted several measures to slow disease transmission and reduce mortality, including closure of all schools and avoidance of large public gatherings, distribution of oseltamivir to all health-care units, publication of specific clinical guidelines, and establishment of a call center to educate members of the public who are seeking health-care information.

United States

After recognition of the first cases of infection with the novel influenza A (H1N1) virus, CDC and state health departments initiated enhanced surveillance measures to identify additional cases. As of May 6, a total of 1,487 confirmed† and probable cases had been reported from 43 states, including 642 confirmed cases (reported from 41 states) and 845 probable cases (reported from 42 states). Current experience with laboratory testing results indicates that the probability of laboratory confirmation for probable cases is >99%. States with the most confirmed cases are Illinois (122 cases), New York (97), California (67), Texas (61), and Arizona (48). Dates of illness onset for patients with confirmed or probable illness range from March 28 to May 4 (Figure 2), although the most recent case counts do not account for testing and reporting delays. Among persons with laboratory-confirmed illness, 35 hospitalized patients have been reported from 16 states, including two patients from Texas who died, both with underlying medical conditions. The age distribution of persons with laboratory-confirmed disease ranged from 3 months to 81 years (Table). A total of 18 patients were aged <2 years, and 31 were aged 2–4 years.

The age distribution of the 35 laboratory-confirmed hospitalized patients ranged from 6 months to 53 years (median: 15 years). Among patients with confirmed disease for whom data were available, 262 (90%) of 292 reported fever, 249 (84%) of 296 reported cough, 176 (61%) of 290 reported sore throat, 65 (26%) of 249 reported diarrhea, and 54 (24%) of 221 reported vomiting.

Other Countries

On April 26, the first cases of novel influenza A (H1N1) virus infection outside of the United States and Mexico were reported in Canada. As of May 6, WHO had reported that 309 persons with laboratory-confirmed disease had been identified in 21 countries other than Mexico and the United States. Confirmed cases have been reported from Asia (Hong Kong S.A.R. and Korea), the Pacific region (New Zealand), the Middle East (Israel), Europe, and Central and South America (El Salvador, Costa Rica, Colombia, and Guatemala) (Figure 3).

Of 178 patients for whom travel history was available, 145 (82%) reported recent travel to Mexico, and four (2%) reported travel to the United States. Among those who had not traveled to Mexico, 17 (52%) reported contact with a returning traveler from Mexico. Canada, Germany, Spain, and the United Kingdom all have reported evidence of in-country, second-generation, human-to-human transmission (e.g., a health-care worker in Germany who had cared for a patient with a confirmed infection). No reports have been made of sustained, community-wide transmission in affected countries. Consistent with cases in North America, most of the cases reported from other countries have been among young adults, with a median age of 27.1 years (range: 2–62 years, N = 45). The majority of cases in other countries have been uncomplicated, and no deaths have been reported; four patients have been hospitalized.

Editorial Note:

Early surveillance data from this outbreak suggest that the novel influenza A (H1N1) virus has the potential for efficient, rapid spread among countries. Although the illness associated with infection generally seems self-limited and uncomplicated, a substantial number of cases of severe disease and death has been reported in previously healthy young adults and children. Several characteristics of this outbreak appear unusual compared with a typical influenza seasonal outbreak. First, the percentage of patients requiring hospitalization appears to be higher than would be expected during a typical influenza season (3). Second, the age distribution of hospitalizations for novel influenza A (H1N1) virus infection is different than that of hospitalizations for seasonal influenza, which typically occur among children aged <2 years, adults aged ≥65 years, and persons with chronic health conditions (3). In Mexico and the United States, the percentage of patients requiring hospitalization has been particularly high among persons aged 30–44 years.

Two deaths have been reported in the United States, resulting in a preliminary case-fatality rate of 0.2% among patients with laboratory-confirmed disease. However, such case-fatality rates should be viewed with caution. The actual case-fatality rate is difficult to ascertain in a rapidly evolving outbreak because an unknown proportion of currently infected patients might die, denominators might be uncertain because of unreported cases, and groups at high risk for death from seasonal influenza (e.g., older adults and patients with chronic disease) might not yet have been exposed to the novel influenza A (H1N1) virus.

Summertime influenza outbreaks in temperate climates have been reported in closed communities such as prisons, nursing homes, cruise ships, and other settings with close contact (4–8). Such outbreaks typically do not result in community-wide transmission, but they can be important indicators of viruses likely to circulate in the upcoming influenza season (8). The novel influenza A (H1N1) virus has been circulating in North America largely after the peak influenza transmission season. For that reason, the epidemiology and severity of the upcoming influenza season in the southern hemisphere or in the northern hemisphere cannot be predicted. The imminent onset of the season for influenza virus transmission in the southern hemisphere, coupled with detection of confirmed cases in several countries in the southern zone, raise concern that spread of novel influenza A (H1N1) virus might result in large-scale outbreaks during upcoming months. Countries in the southern hemisphere that are entering the influenza season should anticipate outbreaks and enhance surveillance accordingly. Influenza virus can circulate year round in tropical regions; therefore, these countries should maintain enhanced surveillance for novel influenza A (H1N1) virus.

Studies in countries affected by the novel influenza A (H1N1) virus should help guide surveillance, case management, and prevention strategies in countries not yet affected. Key concerns that should be addressed in these studies include assessment of the potential impact on public health; clinical progression of disease, including rates and types of complications for different age and risk groups; and information on virus transmissibility. Assessment of potential disease severity associated with this novel virus will help inform decisions on prevention strategies to slow the spread of infection. Effective control measures will depend on the ability of national governments to quickly gather and share virologic, epidemiologic, and clinical information from multiple sources as new cases appear.

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Background

The novel H1N1 flu virus is causing illness in infected persons in the United States and countries around the world. CDC expects that illnesses may continue for some time. As a result, you or people around you may become ill. If so, you need to recognize the symptoms and know what to do.

Symptoms

Common symptoms include fever, headache, tiredness, cough, sore throat, runny nose, body aches, diarrhea, and vomiting. The high risk groups for novel H1N1 flu are not known at this time but it’s possible that they may be the same as for seasonal influenza. People at higher risk of serious complications from seasonal flu include people age 65 years and older, children younger than 5 years old, pregnant women, people of any age with chronic medical conditions (such as asthma, diabetes, or heart disease), and people who are immunosuppressed (e.g., taking immunosuppressive medications, infected with HIV).

Avoid Contact With Others

If you are sick, you may be ill for a week or longer. You should stay home and avoid contact with other persons, except to seek medical care. If you leave the house to seek medical care, wear a mask or cover your coughs and sneezes with a tissue. In general you should avoid contact with other people as much as possible to keep from spreading your illness. At the current time, CDC believes that this virus has the same properties in terms of spread as seasonal flu viruses. With seasonal flu, studies have shown that people may be contagious from one day before they develop symptoms to up to 7 days after they get sick. Children, especially younger children, might potentially be contagious for longer periods.

Treatment is Available for Those Who Are Seriously III

It is expected that most people will recover without needing medical care.

If you have severe illness or you are at high risk for flu complications, contact your health care provider or seek medical care. Your health care provider will determine whether flu testing or treatment is needed. Be aware that if the flu becomes wide spread, there will be little need to continue testing people, so your health care provider may decide not to test for the flu virus.

Antiviral drugs can be given to treat those who become severely ill with influenza. These antiviral drugs are prescription medicines (pills, liquid or an inhaler) with activity against influenza viruses, including H1N1 flu virus. These medications must be prescribed by a health care professional.

There are two influenza antiviral medications that are recommended for use against H1N1 flu. The drugs that are used for treating H1N1 flu are called oseltamivir (trade name Tamiflu ®) and zanamivir (Relenza ®). As the H1N1 flu spreads, these antiviral drugs may become in short supply. Therefore, the drugs will be given first to those people who have been hospitalized or are at high risk of complications. The drugs work best if given within 2 days of becoming ill, but may be given later if illness is severe or for those at a high risk for complications.

Emergency Warning Signs

If you become ill and experience any of the following warning signs, seek emergency medical care.

In children emergency warning signs that need urgent medical attention include:

• Fast breathing or trouble breathing
• Bluish or gray skin color
• Not drinking enough fluids
• Severe or persistent vomiting
• Not waking up or not interacting
• Being so irritable that the child does not want to be held
• Flu-like symptoms improve but then return with fever and worse cough

In adults, emergency warning signs that need urgent medical attention include:

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Sudden dizziness
• Confusion
• Severe or persistent vomiting
• Flu-like symptoms improve but then return with fever and worse cough

Protect Yourself, Your Family, and Community

• Stay informed. Health officials will provide additional information as it becomes available. Visit the CDC H1N1 Flu website.
• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
• Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hand cleaners are also effective.
• Avoid touching your eyes, nose or mouth. Germs spread this way.
• Try to avoid close contact with sick people.
• If you are sick with a flu-like illness, stay home for 7 days after your symptoms begin or until you have been symptom-free for 24 hours, whichever is longer. Keep away from other household members as much as possible. This is to keep you from infecting others and spreading the virus further.
• Learn more about how to take care of someone who is ill in “Taking Care of a Sick Person in Your Home“
• Follow public health advice regarding school closures, avoiding crowds, and other social distancing measures.
• If you don’t have one yet, consider developing a family emergency plan as a precaution. This should include storing a supply of extra food, medicines, and other essential supplies. Further information can be found in the “Flu Planning Checklist”

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The U.N. World Health Organization and U.S. Centers for Disease Control and Prevention have been collecting samples of the new H1N1 swine flu virus to make a new vaccine in case it is needed.

Following are some facts about influenza vaccines.

* The WHO and CDC prepare samples of virus to give to industrial makers.

* These samples must be grown in specially produced chicken eggs. The virus is then purified and made into vaccines, a process that takes months.

* At least 20 companies make flu vaccines including Sanofi Pasteur, Australia’s CSL Ltd, GlaxoSmithKline Plc, Novartis AG, Baxter and nasal spray maker MedImmune, acquired by AstraZeneca Plc.

* Experts agree the current process for making vaccines is clumsy and outdated, but new and more efficient technologies are still a few years away.

* WHO and CDC experts are trying to decide if a new vaccine for the H1N1 swine flu strain is needed, or perhaps if a fourth element could be added to the seasonal flu vaccine mix for next September.

* The health agencies also had been considering adding some vaccines against H5N1 avian influenza, which occasionally infects people and is also considered a major pandemic threat.

* Tests show the H1N1 component of the current seasonal flu vaccine does not protect against the new strain.

* Consulting firm Oliver Wyman found that drug companies would need four years to meet global demand for vaccines if a pandemic broke out today, but new technology could significantly boost production by 2014.

* Currently, drug makers could make up to 2.5 billion doses of pandemic vaccines in one year, meaning it would take four years to meet global demand, Oliver Wyman found. In a best-case scenario, they could make 7.7 billion doses in 1.5 years.

* Compounds called adjuvants can be used to boost a vaccine’s effectiveness, so it could be diluted and used in more people.

* Current global demand for seasonal influenza vaccine is about 500 million doses a year.

* The CDC recommends that 261 million Americans — 85 percent of the population — should be vaccinated against flu. A RAND Corp. study in December showed that only about a third of those who should have did get the vaccine.

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In the 2009 revision of the phase descriptions, WHO has retained the use of a six-phased approach for easy incorporation of new recommendations and approaches into existing national preparedness and response plans. The grouping and description of pandemic phases have been revised to make them easier to understand, more precise, and based upon observable phenomena. Phases 1–3 correlate with preparedness, including capacity development and response planning activities, while Phases 4–6 clearly signal the need for response and mitigation efforts. Furthermore, periods after the first pandemic wave are elaborated to facilitate post pandemic recovery activities.

The current WHO phase of pandemic alert is 5.

In nature, influenza viruses circulate continuously among animals, especially birds. Even though such viruses might theoretically develop into pandemic viruses, in Phase 1 no viruses circulating among animals have been reported to cause infections in humans.

In Phase 2 an animal influenza virus circulating among domesticated or wild animals is known to have caused infection in humans, and is therefore considered a potential pandemic threat.

In Phase 3, an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.

Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Any country that suspects or has verified such an event should urgently consult with WHO so that the situation can be jointly assessed and a decision made by the affected country if implementation of a rapid pandemic containment operation is warranted. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.

Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.

Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.

During the post-peak period, pandemic disease levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave.

Previous pandemics have been characterized by waves of activity spread over months. Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave. Pandemic waves can be separated by months and an immediate “at-ease” signal may be premature.

In the post-pandemic period, influenza disease activity will have returned to levels normally seen for seasonal influenza. It is expected that the pandemic virus will behave as a seasonal influenza A virus. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.

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China denied discrimination lay behind its confinement of scores of Mexican nationals over fears of H1N1 flu, urging Mexico to respond calmly and cooperate in fighting the virus.

Mexican Foreign Minister Patricia Espinosa accused China at the weekend of discriminating against his country’s citizens after Beijing ordered dozens of them into isolation in hotels and other sites across the country, although only one, a man now in Hong Kong, has been found to have the H1N1 flu.

Chinese Foreign Ministry spokesman Ma Zhaoxu rejected the criticism, saying the isolation was correct procedure, not bigotry.

“The measures concerned are not directed at Mexican citizens and there is no discrimination,” Ma said in a statement issued on the ministry website (www.mfa.gov.cn).

“This was purely a medical quarantine issue,” Ma said, adding that Mexico should “give full understanding to the measures adopted by China and handle this matter objectively and calmly.”

A spokeswoman for the Mexican Embassy in Beijing said neither she nor the ambassador had any immediate comment on the Chinese statement. She said that as of Sunday about 70 Mexican nationals were held in confinement in China.

The row over confinement has strained what has been a warming relationship between the two countries, but with Beijing courting Latin America as a trade and diplomatic partner, the damage appears unlikely to last.

Mexico is China’s second biggest trade partner in Latin America — behind Brazil — and its biggest export market there, according to Chinese statistics.

In 2008, their bilateral trade reached $17.6 billion in value, a rise of 17.3 percent on 2007, with China having a big surplus based on electronics, textiles and other consumer goods.

Mexico said on Sunday that its swine flu epidemic had passed the worst and experts said the virus might be no more severe than normal flu.

Mexican Ambassador Jorge Guajardo on Sunday visited a hotel in Beijing where more than 10 Mexicans have been held, but was not allowed to see them, an embassy official said that day.

Mexicans were being held in hotels and other sites across several parts of China, including Hong Kong, said the embassy official.

China’s vast population and patchy medical infrastructure make it particularly vulnerable should the virus take hold.

The Mexican with the H1N1 virus arrived in Hong Kong from Mexico on Thursday following a stopover in Shanghai.

Many of the confined Mexicans were on that same flight to Shanghai, but others had reached China on flights from Los Angeles, Newark and Vancouver, said the embassy official.

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What if I get this new virus and I am pregnant?

We don’t know if this virus will cause pregnant women to have a greater chance of getting sick or have serious problems. We also do not know how this virus will affect the baby.

We do know that pregnant women are more likely to get sick than others and have more serious problems with seasonal flu. These problems may include early labor or severe pneumonia. We don’t know if this virus will do the same, but it should be taken very seriously.

What can I do to protect myself, my baby and my family?

Take these everyday steps to help prevent the spread of germs and protect your health:

• Cover your nose and mouth with a tissue when you cough or sneeze, or sneeze into your sleeve. Throw the tissue in the trash after you use it.
• Wash your hands often with soap and warm water, especially after you cough or sneeze. Alcohol-based gel hand cleaners are also good to use.*
• Avoid touching your eyes, nose or mouth. Germs spread this way.
• Try to avoid close contact with sick people. (If you are pregnant and you live or have close contact with someone who has H1N1 flu, talk to your doctor about medicines to prevent flu.)
• Have a plan to care for sick family members.
• Stock up on household, health, and emergency supplies, such as water, Tylenol®, non-perishable foods.

What are the symptoms of H1N1?

Symptoms are like seasonal flu and include the following:

• Fever
• Cough
• Sore throat
• Body aches
• Headaches
• Chills and fatigue
• Sometimes, diarrhea and vomiting

What should I do if I get sick?

• If there is H1N1 flu in your community pay extra attention to your body and how you are feeling.
• If you get sick with flu-like symptoms, stay home, limit contact with others, and call your doctor. Your doctor will decide if testing or treatment is needed. Tests may include a nasal swab which is best to do within the first 4-5 days of getting sick. Like regular flu, H1N1 flu may make other medical problems worse.
• If you are alone at any time, have someone check in with you often if you are feeling ill. This is always a good idea.
• If you have close contact with someone who has H1N1 flu or is being treated for exposure to H1N1 flu, contact your doctor to discuss whether you need treatment to reduce your chances of getting the flu.

How is H1N1 flu treated?

• Treat any fever right away. Tylenol® (acetaminophen) is the best treatment of fever in pregnancy.
• Drink plenty of fluids to replace those you lose when you are sick.
• Your doctor will decide if you need antiviral drugs such as Tamiflu® (oseltamivir) or Relenza® (zanamivir). Antiviral drugs are prescription pills, liquids or inhalers that fight against the flu by keeping the germs from growing in your body. These medicines can make you feel better faster and make your symptoms milder.
• These medicines work best when started soon after symptoms begin (within two 2 days), but they may also be given to very sick or high risk people (like pregnant women) even after 48 hours. Antiviral treatment is taken for 5 days.
• Tamiflu® and Relenza® are also used to prevent H1N1 flu and are taken for 10 days.
• There is little information about the effect of antiviral drugs in pregnant women or their babies, but no serious side effects have been reported. If you do think you have had a side effect to antiviral drugs, call your doctor right away.

When should I get emergency medical care?

If you have any of these signs, seek emergency medical care right away:

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Sudden dizziness
• Confusion
• Severe or persistent vomiting
• Decreased or no movement of your baby
• A high fever that is not responding to Tylenol®

How should I feed my baby?

Flu can be very serious in young babies. Babies who are breastfed do not get as sick and are sick less often from the flu, than do babies who are not breastfed.

Breastfeeding protects babies. Breast milk passes on antibodies from the mother to a baby. Antibodies help fight off infection.

Is it ok to breastfeed my baby if I am sick?

• A mother’s milk is made to fight diseases in her baby. This is really important in young babies when their immune system is still growing.
• Do not stop breastfeeding if you are ill. Breastfeed early and often. Limit formula feeds if you can. This will help protect your baby from infection.
• Be careful not to cough or sneeze in the baby’s face, wash your hands often with soap and water
• Your doctor might ask you to wear a mask to keep from spreading this new virus to your baby
• If you are too sick to breastfeed, pump and have someone give the expressed milk to your baby.

Is it OK to take medicine to treat or prevent H1N1 flu while breastfeeding?

Yes. Mothers who are breastfeeding can continue to nurse their babies while being treated for the flu.

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Offices and businesses stayed closed in Mexico on Monday to try to prevent the spread of a deadly new strain of flu, and authorities said the battle was being won with a sharp drop in new cases.

Outside Mexico, however, the number of confirmed cases continues to rise, and officials say it will take time to confirm just how contagious and dangerous the virus is.

Mexico’s health ministry announced on Sunday the flu epidemic had passed the worst and experts said the virus might be no more severe than normal flu, although it could still have an impact on world health and was expected to spread to more countries.

“The virus has entered into a stabilization phase. The cases are starting to decrease,” Mexican President Felipe Calderon said, adding that Mexico would begin to get back on its feet again this week after shutting restaurants, offices, cinemas and even churches to try to stop the spread of the disease.

“Our objective is to return to normality as soon as possible but what I want is to do that in secure conditions,” Calderon said in a televised interview late on Sunday.

After days of alarm that had kept streets eerily quiet, Mexico City appeared more relaxed, with some people venturing out on bikes or running. Many no longer wore the surgical masks that have been almost obligatory in the city in the last week.

Laboratory tests have shown 590 firm cases of the virus in Mexico, out of which 22 people were confirmed to have died.

The World Health Organization said its laboratories had identified a total of 898 H1N1 flu infections in 18 countries. Its toll lags national reports but is considered more scientifically secure.

In Turkey, a hospital spokesman denied that one of its patients had been killed by the new strain. Broadcaster CNN Turk had earlier reported that a patient had died of suspected swine flu at Akdeniz Hospital in the south of the country.

Only one death has been confirmed outside Mexico — a Mexican toddler who was visiting the United States.

FLU SPREADS IN UNITED STATES

In the United States, the flu has spread to 30 states and infected 226 people, the U.S. Centers for Disease Control and Prevention said. It seems to be hitting mostly younger people, with very few cases among those over 50 years old.

CDC acting director Richard Besser said there were “encouraging signs” the new strain was not more severe than what would be seen during normal seasonal flu, but he still expected the new virus to have a significant impact on health.

“We’re not out of the woods,” Besser told “Fox News Sunday.

The U.S. government said it hoped to have a vaccine ready for the new flu strain by the autumn.

The WHO said flu surveillance should be increased in humans and animals now that the latest H1N1 strain was found to have infected pigs in Canada. A traveler carried the virus from Mexico to Canada and infected his family and a herd of swine.

Few countries are ready to take chances with the new virus, widely dubbed swine flu.

Action by Chinese authorities to hold Mexicans in hotels and other places, whether they were ill or not, sparked a diplomatic dispute with Mexico.

A Mexican Embassy official in China said Chinese authorities were quarantining more than 50 Mexican business people and tourists after some showed flu symptoms. [nPEK8030]

China denied Mexican complaints that discrimination lay behind the measures.

Asia’s trade and tourism could be hit by the latest flu outbreak but lessons learned from the SARS epidemic in 2003 are boosting efforts to counter the effects. SARS, or severe acute respiratory syndrome, killed more than 800 people around the world in 2003 after first appearing in southern China.

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Q: Please give us basic information on the ongoing swine flu epidemic that is threatening to become a pandemic. What causes it? What can we do to prevent it? If a person has been vaccinated with flu vaccine, is he/she immune from the disease?
–Cynthia R., Manila

A: Swine influenza or swine flu is a highly contagious and often fatal acute respiratory infection of pigs that is caused by any of a number of strains (types) of the influenza A virus.

A swine influenza virus normally affects pigs only. But in the presence of other strains of the virus in the same pig, it can swap genes with the other strains and mutate to a form that can jump species and affect humans. The current swine flu outbreak is caused by a new H1N1 strain of the swine virus that has done exactly that.

The new H1N1 strain was first noticed after a woman died in the southern state of Oaxaca, Mexico on April 13. Since then, the epidemic has evolved rapidly. As of April 28, Mexico has reported nearly 2,000 cases of the disease in humans that have resulted in 152 deaths. Six other countries have officially reported confirmed cases of the disease, but with no deaths: US, Canada, New Zealand, the United Kingdom, Israel and Spain.

The current swine flu epidemic has a greater chance of becoming a pandemic than the bird flu outbreak that has been going around the last few years, because the swine flu virus has been verified to be capable of sustained human-to-human transmission. 

In humans, the swine flu virus is transmitted by droplets or aerosols that are coughed, sneezed or exhaled by people with the disease. It enters the body via the nose or the mouth. It can also be transmitted by direct contact with secretions from infected people or by touching contaminated objects and then touching the nose or mouth with the hand, but it cannot be transmitted through eating properly cooked pork.

The signs and symptoms of swine flu appear after an incubation period of 24-48 hours. They include fever, cough, runny nose, chills, cough, sore throat, body malaise, muscle pain and headache.

There are two classes of antiviral medicines that are presently used in the treatment of flu but, at present, experts do not have enough information to make recommendations on the use of these antivirals in the treatment of swine flu.

The best way to prevent swine flu is by active immunization or vaccination against the disease. However, and this is in answer to your last question, flu vaccines are strain specific and the current available vaccines are, most likely, ineffective against the swine flu virus. Experts say that it will take 6-7 months to develop a vaccine that is specific for swine flu. So, what can the public do in the meantime?

The following are the recommendations of the World Health Organization (WHO):

• Avoid close contact with people who appear unwell and who have fever and cough. 
• Wash your hands with soap and water frequently and thoroughly. 
• Practice good health habits including adequate sleep, eating nutritious food, and keeping physically active.

If there is an ill person at home:

• Try to provide the ill person a separate section in the house. If this is not possible, keep the patient at least 1 meter in distance from others. 
• Cover mouth and nose when caring for the ill person. Masks can be bought commercially or made using the readily available materials as long as they are disposed of or cleaned properly. 
• Wash your hands with soap and water thoroughly after each contact with the ill person. 
• Try to improve the air flow in the area where the ill person stays. Use doors and windows to take advantage of breezes. 
• Keep the environment clean with readily available household cleaning agents.

swine flu

On April 17, 2009, CDC determined that two cases of febrile respiratory illness occurring in children who resided in adjacent counties in southern California were caused by infection with a swine influenza A (H1N1) virus. The viruses from the two cases are closely related genetically, resistant to amantadine and rimantadine, and contain a unique combination of gene segments that previously has not been reported among swine or human influenza viruses in the United States or elsewhere. Neither child had contact with pigs; the source of the infection is unknown. Investigations to identify the source of infection and to determine whether additional persons have been ill from infection with similar swine influenza viruses are ongoing. This report briefly describes the two cases and the investigations currently under way. Although this is not a new subtype of influenza A in humans, concern exists that this new strain of swine influenza A (H1N1) is substantially different from human influenza A (H1N1) viruses, that a large proportion of the population might be susceptible to infection, and that the seasonal influenza vaccine H1N1 strain might not provide protection. The lack of known exposure to pigs in the two cases increases the possibility that human-to-human transmission of this new influenza virus has occurred. Clinicians should consider animal as well as seasonal influenza virus infections in their differential diagnosis of patients who have febrile respiratory illness and who 1) live in San Diego and Imperial counties or 2) traveled to these counties or were in contact with ill persons from these counties in the 7 days preceding their illness onset, or 3) had recent exposure to pigs. Clinicians who suspect swine influenza virus infections in a patient should obtain a respiratory specimen and contact their state or local health department to facilitate testing at a state public health laboratory.

Case Reports

Patient A. On April 13, 2009, CDC was notified of a case of respiratory illness in a boy aged 10 years who lives in San Diego County, California. The patient had onset of fever, cough, and vomiting on March 30, 2009. He was taken to an outpatient clinic, and a nasopharyngeal swab was collected for testing as part of a clinical study. The boy received symptomatic treatment, and all his symptoms resolved uneventfully within approximately 1 week. The child had not received influenza vaccine during this influenza season. Initial testing at the clinic using an investigational diagnostic device identified an influenza A virus, but the test was negative for human influenza subtypes H1N1, H3N2, and H5N1. The San Diego County Health Department was notified, and per protocol, the specimen was sent for further confirmatory testing to reference laboratories, where the sample was verified to be an unsubtypable influenza A strain. On April 14, 2009, CDC received clinical specimens and determined that the virus was swine influenza A (H1N1). The boy and his family reported that the child had had no exposure to pigs. Investigation of potential animal exposures among the boy’s contacts is continuing. The patient’s mother had respiratory symptoms without fever in the first few days of April 2009, and a brother aged 8 years had a respiratory illness 2 weeks before illness onset in the patient and had a second illness with cough, fever, and rhinorrhea on April 11, 2009. However, no respiratory specimens were collected from either the mother or brother during their acute illnesses. Public health officials are conducting case and contact investigations to determine whether illness has occurred among other relatives and contacts in California, and during the family’s travel to Texas on April 3, 2009.

Patient B. CDC received an influenza specimen on April 17, 2009, that had been forwarded as an unsubtypable influenza A virus from the Naval Health Research Center in San Diego, California. CDC identified this specimen as a swine influenza A (H1N1) virus on April 17, 2009, and notified the California Department of Public Health. The source of the specimen, patient B, is a girl aged 9 years who resides in Imperial County, California, adjacent to San Diego County. On March 28, 2009, she had onset of cough and fever (104.3°F [40.2°C]). She was taken to an outpatient facility that was participating in an influenza surveillance project, treated with amoxicillin/clavulanate potassium and an antihistamine, and has since recovered uneventfully. The child had not received influenza vaccine during this influenza season. The patient and her parents reported no exposure to pigs, although the girl did attend an agricultural fair where pigs were exhibited approximately 4 weeks before illness onset. She reported that she did not see pigs at the fair and went only to the amusement section of the fair. The Imperial County Public Health Department and the California Department of Public Health are now conducting an investigation to determine possible sources of infection and to identify any additional human cases. The patient’s brother aged 13 years had influenza-like symptoms on April 1, 2009, and a male cousin aged 13 years living in the home had influenza-like symptoms on March 25, 2009, 3 days before onset of the patient’s symptoms. The brother and cousin were not tested for influenza at the time of their illnesses.

Epidemiologic and Laboratory Investigations

As of April 21, 2009, no epidemiologic link between patients A and B had been identified, and no additional cases of infection with the identified strain of swine influenza A (H1N1) had been identified. Surveillance data from Imperial and San Diego counties, and from California overall, showed declining influenza activity at the time of the two patients’ illnesses. Case and contact investigations by the county and state departments of health in California and Texas are ongoing. Enhanced surveillance for possible additional cases is being implemented in the area.

Preliminary genetic characterization of the influenza viruses has identified them as swine influenza A (H1N1) viruses. The viruses are similar to each other, and the majority of their genes, including the hemagglutinin (HA) gene, are similar to those of swine influenza viruses that have circulated among U.S. pigs since approximately 1999; however, two genes coding for the neuraminidase (NA) and matrix (M) proteins are similar to corresponding genes of swine influenza viruses of the Eurasian lineage (1). This particular genetic combination of swine influenza virus segments has not been recognized previously among swine or human isolates in the United States, or elsewhere based on analyses of influenza genomic sequences available on GenBank.* Viruses with this combination of genes are not known to be circulating among swine in the United States; however, no formal national surveillance system exists to determine what viruses are prevalent in the U.S. swine population. Recent collaboration between the U.S. Department of Agriculture and CDC has led to development of a pilot swine influenza virus surveillance program to better understand the epidemiology and ecology of swine influenza virus infections in swine and humans.

 The viruses in these two patients demonstrate antiviral resistance to amantadine and rimantadine, and testing to determine susceptibility to the neuraminidase inhibitor drugs oseltamivir and zanamivir is under way. Because these viruses carry a unique combination of genes, no information currently is available regarding the efficiency of transmission in swine or in humans. Investigations to understand transmission of this virus are ongoing.

swine flu