U.S. Declares Public Health Emergency as Swine Flu Outbreak Spreads

On Sunday, April 26, the U.S. Department of Health and Human Services (DHHS) declared a public health emergency related to a growing outbreak of a new strain of swine flu.

The outbreak is associated with an H1N1 strain of influenza A that affects pigs. Pigs can also be infected by avian (bird) and human influenza viruses, and when flu viruses from different species coexist, they can swap gene segments to form "hybrid" viruses. While most prior cases of swine flu in humans have been linked to contact with pigs, the current strain appears to have evolved to be transmissible from person to person. Swine flu is not contracted from eating cooked pork.

Public health officials are concerned about the recent outbreak because most people do not have natural immunity to the new strain and because it is not preventable using current stocks of flu vaccine. The strain is susceptible to the anti-influenza drugs oseltamivir (Tamiflu) and zanamivir (Relenza), but resistant to amantadine (Symmetrel) and rimantadine (Flumadine).

Confirmed cases of swine flu were first reported late last week along the Mexican border in California and Texas. Over the weekend, additional cases were reported in Kansas, Ohio, and among school children in New York City. As of Monday morning, a total of 40 cases had been confirmed in the U.S., 28 of them in New York City.

The U.S. cases are thought to be related to a flu outbreak in Mexico that has caused nearly 2000 cases of illness and about 150 deaths; however, only a small number of the Mexican cases have been confirmed as H1N1 swine flu.

In contrast with most flu epidemics, the recent Mexican cases have tended to affect young, otherwise healthy adults; typically young children, elderly people, and individuals with chronic illnesses and compromised immunity -- including HIV positive people -- are most susceptible to and most likely to develop severe cases and complications of influenza.

One aspect that has puzzled epidemiologists is that while the Mexican outbreak has had a relatively high fatality rate, all the people affected in the U.S. have recovered after a relatively short and mild illness.

Suspected or confirmed cases of swine flu have also been reported in Canada, the U.K., Spain, Israel, and New Zealand, typically among individuals who have recently spent time in Mexico. The World Health Organization (WHO) has called the outbreak a "public health emergency of international concern."

The U.S. public heath emergency declaration releases resources to track and manage the outbreak. At a Sunday press conference, newly appointed Homeland Security Secretary Janet Napolitano sought to allay panic, saying people should view it as a "declaration of emergency preparedness."

As of Monday, the Centers for Disease Control and Prevention (CDC) has not called for extraordinary measures such as restricting travel, closing schools, or canceling public events. Such steps have been taken in Mexico City, however. As the epidemic evolves, public health officials may call for additional precautions in affected communities, including use of face masks and stricter "social distancing" measures.

The CDC has set up a web site with information about the emerging epidemic, at www.cdc.gov/swineflu.

The site includes general information and frequently asked questions about swine flu, the most recent epidemiological data on the current outbreak, basic precautions for flu prevention, and the latest recommendations for clinicians, home care providers, public officials, travelers, and others.

Symptoms of swine flu -- as with influenza in general -- include fever, fatigue, lethargy, lack of appetite, cough, runny nose, difficulty breathing, sore throat, body aches, and in some cases gastrointestinal symptoms such as nausea, vomiting, and diarrhea,

The CDC recommends the following steps for minimizing flu transmission:

• Cover your nose and mouth with a tissue when you cough or sneeze, and throw it in the trash after use.
• Wash your hands frequently with soap and water, or use an alcohol-based hand sanitizer.
• Avoid touching your eyes, nose, and mouth.
• If possible, avoid close contact with sick people.
• If you feel ill, stay home and avoid school, work, public transit, and other places where people gather.

In communities with confirmed swine flu cases, the CDC suggests that, "Persons with underlying medical conditions who are at high risk for complications of influenza may wish to consider avoiding large gatherings." Prophylactic anti-flu medications are recommended for susceptible people who must travel to outbreak areas.

4/28/09

Sources

Centers for Disease Control and Prevention (CDC). Swine Influenza (Flu). Updated April 27, 2009. www.cdc.gov/swineflu.

Associated Press. US declares public health emergency for swine flu. San Francisco Chronicle. April 26, 2009.

CNN. Swine flu sparks global concern; Mexico epicenter of outbreak. CNNhealth.com. April 27, 2009.