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Get the FactsFacts about influenza and avian fluFluWhat is influenza (the “flu”)? Prevent the seasonal flu: get vaccinated. Flu PandemicHow are the seasonal flu and pandemic flu different? What are the effects of a flu pandemic? What are the symptoms of a pandemic flu infection? Will there be a vaccine available for pandemic flu? How is the United States preparing for the next flu pandemic? Avian FluWhat is the avian influenza (bird flu)? The current outbreak in birds. Is there a test for the bird flu? Is there a bird flu vaccine yet? Is there a drug to treat or prevent the flu? FluWhat is influenza (the “flu”)? The seasonal flu is a contagious respiratory illness caused by influenza viruses. It usually causes a mild to severe illness and, less commonly, can lead to death. The best way to prevent catching the flu is by getting a flu shot each fall. The flu season in the U.S. usually lasts from December through March. Every year in the United States, approximately 36,000 people die from flu-related complications. The symptoms of flu include fever, headache, cough, sore throat, chills, and muscle aches. Some people, such as the elderly, young children, and people with certain health conditions, are at high risk for serious flu complications. These can include bacterial pneumonia, dehydration, or worsening of chronic conditions such as heart problems or diabetes. Children can also have gastrointestinal symptoms, such as nausea, vomiting, and diarrhea, but these symptoms are uncommon in adults. Most people, however, recover from the seasonal flu within a two-week period.
How the flu spreads. Flu viruses spread from person to person in respiratory airborne droplets caused by coughing and sneezing. Sometimes people become infected by touching something (i.e., a door knob or other surface) contaminated with flu viruses and then touching their mouth or nose. Prevent the seasonal flu — get vaccinated. The single best way to prevent the seasonal flu is to get a flu vaccination each fall, between October and November. There are two types of vaccines:
About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Seasonal flu vaccines will not protect against influenza-like illnesses caused by other viruses or protect against other influenza strains not in the current vaccine, such as avian flu. You can learn more about seasonal flu by visiting the Centers for Disease Control and Prevention (CDC) website.
Influenza ABCs. There are three main classes of influenza viruses: A, B, and C. Most human cases of flu illness are Type A or Type B, with A being more common. Influenza viruses also infect birds, pigs, horses, and other mammals — in fact some kinds of flu are mainly animal illnesses. In the past, where historical information is available, human pandemics have been Type A flu viruses.
There are many subtypes of the Type A influenza viruses. They differ because of variations in certain proteins on the surface of the influenza A virus called H (hemagglutinin) and N (neuraminidase) proteins. There are 16 known H subtypes and nine known N subtypes of influenza A viruses. Many different combinations of H and N proteins, and therefore many different subtypes, are possible. The influenza virus commonly changes from year to year, developing new subtypes. Flu PandemicWhat is flu “pandemic”? A flu pandemic is a global outbreak of influenza, according to the CDC. A flu pandemic happens when a novel (new) influenza virus emerges. This is called “antigenic shift” — where a sudden change causes this virus to infect humans effectively. The virus becomes highly infectious and contagious in humans. No prior immunity would exist from exposure to seasonal influenza, and no vaccine would be available for wide distribution. It can spread easily from person to person, cause serious illness and death, and can sweep across the country and around the world in very short time. Three conditions must be met for a human pandemic to start:
The H5N1 influenza virus (also called avian or bird flu) is currently spreading through wild birds and poultry in Asia, Europe, the Middle East, and Africa. So far, it has met the first two criteria of a human pandemic — it’s a new virus that can infect humans, and it has caused rare cases of serious illness and death. However, to date, it has not met the third criteria. It has not been easily transmitted from human to human.
How are the seasonal flu and pandemic flu different?
For additional information on seasonal flu, visit www.hhs.gov/flu. What are the effects of a flu pandemic? A flu pandemic will have a significant impact on society. A pandemic could result in a large number of people falling ill, including children and young adults, with many deaths. A pandemic could also require restrictions on travel, alterations to normal business operations, and dismissal of students from school to help slow the spread of infection. The United States was overwhelmed by the 1918–1919 flu pandemic, which caused the deaths of at least 675,000 Americans. If a pandemic of similar severity occurred today, 90 million Americans could become ill, and approximately two million Americans could die. In addition to the impact on human health, a flu pandemic presents a major threat to the world economy. What are the symptoms of a pandemic flu infection? The symptoms of a pandemic flu infection will likely be similar to those of seasonal flu, but they may last longer and be more severe. Will there be a vaccine available for pandemic flu? A vaccine for pandemic flu may not be available for 4–6 months after a pandemic starts, and even then, it may be available only in limited amounts. How is the United States preparing for the next flu pandemic? The United States is working with other nations and the World Health Organization (WHO) to strengthen systems to detect and contain outbreaks of viruses that may cause a pandemic. WHO uses a series of six phases of pandemic alert to inform the world of the seriousness of the threat and of the need for progressively more intense preparedness. World Health Organization Pandemic Alert Phases
The world is currently in Phase Three, a new influenza virus subtype is causing disease in humans, but is not yet spreading efficiently and substantially among humans.
Avian FluWhat is the avian influenza (bird flu)? There are many types of avian influenza viruses that occur naturally in wild birds — such as ducks, swans, and geese — in all regions of the world. Waterfowl have probably carried these viruses for centuries. The virus is carried in the bird’s respiratory and digestive systems. These viruses are highly contagious between birds. Some strains do not make the birds sick, but other strains can kill them.
How is the avian flu spread? These viruses are spread as wild birds, following their normal migration routes, come in contact with other wild birds or domestic poultry. The virus is spread through saliva, nasal secretions, and feces of infected birds. As the influenza viruses are spread to susceptible birds, they cause two forms of the disease. The “low pathogenic” form may go undetected, causing only mild symptoms (such as ruffled feathers or a reduction in egg production). The “highly pathogenic” form can spread rapidly through flocks of poultry. This form can have a high mortality rate that can reach 90–100 percent, often within 48 hours. Domesticated birds can become infected with the avian influenza virus when they come in direct contact with another infected bird, contaminated surfaces (dirt, equipment, or cages), or material (water or feed).
The current outbreak in birds. The current outbreak of the avian influenza virus is a Type A flu virus of the subtype H5N1 and has been identified in birds in certain countries in Asia, Europe, the Middle East, and Africa. More than 200 million birds have died or been culled (selected for slaughter) in order to contain the spread in the bird population. Worldwide public health professionals and scientists are closely monitoring the situation.
Why the concern? The avian influenza A (H5N1) strains have raised concerns because they continue to evolve, are very contagious in birds, and have been transmitted, in limited circumstances, to other animals and humans. Therefore, public health officials are closely monitoring the spread of the virus. In the 20th century, there have been three flu pandemics which were all caused by Type A influenza viruses: the 1918-19 “Spanish flu” [A (H1N1)], which caused the highest number of known influenza deaths; the 1957-58 “Asian flu” [A (H2N2)]; and the 1968-69
“ While the avian influenza A (H5N1) usually does not affect humans, more than 260 human cases have been reported between January 2003–2007, mostly in Asia. More than half of those affected have died.* WHO maintains situation updates and reports on human cases of the avian flu. Most of these human cases have occurred from direct or close contact with infected poultry or contaminated surfaces. In very rare cases, the avian flu virus has spread from one person with the avian flu to another person, but transmission has been limited, inefficient, and unsustained. Scientists are also investigating why a majority of the cases and deaths occur in younger, healthy groups. As stated previously, this characteristic differs from the seasonal flu.
Is there a test for the bird flu? In 2006, the FDA approved a newly developed laboratory test to diagnose H5 (Asian lineage) strains of influenza. This test is indicated in people with symptoms of severe respiratory illness and a risk of exposure to infected poultry in a country with H5N1 influenza outbreaks. If the test results indicate the presence of H5, then further testing is required to identify the N (neuraminidase) subtype. The CDC recommends that influenza A/H5 testing be performed on a case-by-case basis and in consultation with the local or state health department. If a health care provider suspects any patient is infected with avian influenza, he or she should contact the state or local health department immediately.
Is there a bird flu vaccine yet? Currently, there is no vaccine readily available to protect humans against the H5N1 avian influenza virus. Research studies to test a vaccine to protect humans against the H5N1 virus began in 2005, and clinical trials are currently under way. The U.S. government has awarded contracts to several vaccine manufacturers to expedite the development and production of the avian influenza vaccine supply. In the event of a flu pandemic, government public health agencies would likely issue guidelines on who should get any vaccine that might be available at that time and may also play a role in vaccine distribution.
Is there a drug to treat or prevent the flu? Antivirals are types of drugs that may help prevent or treat viral infection. There are several drugs that have been used to prevent or treat seasonal flu. Their effectiveness in avian flu is not yet known. There is not a sufficient supply of antiviral drugs to prevent flu in the whole population, and, for treatment, they likely work best if given within the first 48 hours of a flu infection. In the event of widespread seasonal flu or a flu pandemic, government public health agencies would likely issue guidelines on who should receive antiviral drugs and may play a role in their distribution. It is unlikely that these drugs would substantially modify the course or effectively contain the spread of an influenza pandemic. * WHO only reports laboratory-confirmed cases. |