Avian—or bird—influenza is a respiratory infection caused by the H5N1 virus, which normally only infects birds and pigs. Avian flu often causes no symptoms in wild birds, but can kill chickens, turkeys, and other domesticated poultry.
Since 1997 more than 100 people have become ill from avian influenza and about half of these people have died. Most people who became infected had close contact with infected birds. In a few cases the infection spread from the ill person to someone else, but it did not continue beyond that person. Avian flu has infected humans in Asia and Eastern Europe, and experts worry that it may become a pandemic, or worldwide outbreak, with the potential to kill seven million people or more.
Historically, an average of three influenza pandemics has occurred each century, though some (like the most recent one in 1968) have been relatively mild. Experts cannot predict whether or not avian flu will someday become a human pandemic. They are confident, however, that pandemic flu will return in some form relatively early in this century. The information in this article focuses on avian flu, but it likely applies to any pandemic flu virus that may emerge–whether or not it is of avian origin.
Experts believe that if the avian flu virus becomes capable of spreading from person to person, it could cause a severe pandemic. Other flu viruses—such as the ones that cause seasonal influenza, or “the flu,” have the ability to shift features due to mutations—or changes—in their genes. If a person was infected simultaneously with the avian flu virus and one of the human flu viruses, experts believe that the viruses could swap genes, creating avian flu viruses that could easily spread from person to person. Avian flu is also a threat because—unlike seasonal influenza—it commonly causes life-threatening pneumonia and other serious complications, even among young, healthy individuals.
Antibodies are the body’s natural defense against infection. Vaccines work by triggering the body to make specific antibodies to a particular virus. If a person who has been vaccinated becomes infected with the virus, the antibodies destroy it. The vaccine against seasonal flu is effective at reducing the spread of seasonal flu but not avian flu, because it triggers antibodies to a different virus.
Research studies in humans began in April 2005 to evaluate vaccines to prevent avian flu. To increase the availability of vaccine, researchers are also studying ways to make smaller doses more effective. Results from the first of these studies should be available sometime in 2006.
Experts concede, however, that even if the vaccine works well now, it may not be effective for preventing a pandemic if the virus changes. In that case, a new vaccine will be needed, and making it will take weeks or months. Researchers hope that even if the vaccine under study isn’t effective, the process of creating it will better prepare manufacturers and vaccine experts for creating another one.
In light of the current concerns about avian flu, governmental agencies have outlined steps to prevent the spread of infection if a pandemic occurs. These steps include measures that reduce group activities, such as “snow days,” voluntary quarantine, and in extreme situations, mandatory quarantine.
In addition, medications used to prevent seasonal flu may be effective against avian flu. Experts believe that two of the four available prescription flu medications, Tamiflu (oseltamivir) and Relenza (zanamivir), may be effective but need further study. The federal government has begun storing these medications in case of a pandemic.
As of October 2005, the Department National Strategic Stockpile contained 2.3 million doses of Tamiflu and 84,000 doses of Relenza. These doses are sufficient to treat 234,200 adults according to current nonpandemic influenza recommendations for dosage and length of treatment. It is not yet known whether treating pandemic influenza–if effective at all–will require higher doses or longer treatment periods. The Department of Health and Human Services continues to purchase additional doses to add to the stockpile, though supplies remain limited.
So, will a vaccine be ready if an avian flu pandemic hits? No one knows for sure, but experts agree that vaccine research and advance planning are critical for reducing the impact of worldwide infection.
