Questions and Answers about Avian Influenza
The following questions and answers were compiled by science writers in the UC Davis News Service, based on interviews with these UC Davis experts in human and animal health and medicine:
--Christian Sandrock, a physician and assistant professor of pulmonary and critical care medicine, and an expert in disaster preparedness, emerging infectious diseases, terrorism and other threats to public health;
--Carol Cardona, associate professor and Cooperative Extension poultry veterinarian in the UC Davis School of Veterinary Medicine, and an expert in surveillance for and detection of avian influenza in domestic poultry;
--Walter Boyce, professor and director of the Wildlife Health Center in the UC Davis School of Veterinary Medicine, and an expert in disease transmission among wild birds and other animals.
What is avian influenza, or "bird flu"?
It is a disease, caused by an influenza A virus, that occurs in bird species. The natural reservoirs for the virus are wild waterfowl and shorebirds, particularly ducks and geese. It usually is not deadly in wild birds. There are several strains, or types, of avian influenza virus. Public health officials and researchers keep track of the strains by giving them names with individual H and N designations, such as H5N1.
How does avian influenza spread?
Wild birds may have influenza viruses in their digestive tracts. The virus is shed in their wastes into water where the birds congregate and thereby spreads to other wild birds. It also can spread via waste matter from wild birds to domestic birds, such as chickens and ducks, through contaminated water or food. In domestic birds (poultry), certain types of avian influenza can be deadly. When these deadly strains of avian flu erupt in poultry flocks, animal health authorities may order that all the poultry in the area be surveyed, killed and buried or burned, to stop the chain of infection.
Is avian influenza found in animals other than birds?
It has been found in domestic pigs, as pigs are susceptible to both the avian and human strains of influenza. It has been found rarely in some other mammal species. Most influenza experts think the virus traveled to pigs from infected domestic poultry in parts of Asia where poultry and pigs are often housed in close quarters. Avian flu also has infected zoo tigers and leopards in Asia that were fed raw infected chickens.
Is avian influenza found in people?
One particularly serious strain of avian influenza currently circulating in Asia, named H5N1, was first diagnosed in a person in Hong Kong 1997, and 59 people in Southeast Asia are known to have died from it since late 2003. Influenza researchers note that most of the people who got infected, with a few possible exceptions, were infected by domestic poultry. In the exceptions, there was very close contact: in one a mother who had close contact with her sick daughter died of the same strain of influenza, and two members of a family in Indonesia are being investigated as possible cases of human-to-human transmission.
If relatively few people have died, why are experts worried?
In people, human influenza virus is a regular seasonal health problem. Every year it kills about 36,000 people in the United States. It has also been the cause of pandemics, three in the 20th century alone. Much of influenza's persistence and severity is due to its extraordinary ability to mutate, or genetically rearrange itself. Today scientists and health officials are very concerned that an avian influenza virus -- maybe H5N1 -- and some other influenza virus could combine into a new, very dangerous influenza virus -- one that could have a high death rate and could also spread between people easily. If such a virus emerged, it could cause a pandemic rivaling the great influenza pandemic of 1918-19, which killed 40 million to 50 million people.
Why are the experts more worried now than they were?
First, H5N1 has killed half the people known to be infected. That is extraordinary for an influenza virus. (For comparison, in the great pandemic of 1918-1919, the virus killed about 1 of 50 people infected; typical seasonal influenza kills about 1 of 1,000 people infected. Second, with the world's rising population and ease of international travel, the conditions are ideal for the virus to rapidly travel around the world -- via a person flying from one country to another, or via trade in domestic poultry or fighting birds, or via wild birds that migrate thousands of miles twice a year. Finally, influenza preparedness, surveillance and prevention are lagging in some countries, and this may hasten the emergence and spread of a pandemic virus.
What impact would a pandemic have on our communities and economy?
Avian influenza's most obvious impacts so far have been in agricultural economies. In Asia, death from the disease or government-ordered slaughter has killed an estimated 130 million chickens and other poultry, with devastating economic effects on farmers. In the United States, although most poultry are not raised under the same conditions as in Asia, it is possible that avian influenza could erupt in commercial flocks.
In the general public, a human pandemic could be devastating to communities and economies. While it is impossible to predict accurately how dangerous a pandemic might be, some experts say that 20 percent to 30 percent of the world's population of 6.4 billion people could become ill, with millions of them dying. And pandemic influenza tends to be different from seasonal influenza, which tends to affect the elderly and the sick more than other people. Pandemic influenza, on the other hand, historically has affected healthy adults who are young or middle-aged. The effect of such an illness on the workforce would be tremendous.
If a pandemic developed, public health officials would recommend or order actions to reduce the spread of the disease. People might be asked to stay home from work; schools might be closed temporarily; large gatherings might be canceled and travel could be restricted. If great numbers of people fell ill, the flow of basic needs, supplies and services might be interrupted.
How can I keep my family and myself safe from avian influenza?
It sounds strange in the face of such a frightening threat, but one thing everyone can do to reduce the risk of an influenza pandemic is very simple: Wash your hands. Use warm water and soap; rub your hands together vigorously for 30 seconds, and do it several times daily. Alternatively, use an alcohol-based antiseptic gel or wash in the place of hand washing. These products are sold at drug stores and supermarkets; be sure to use only those that contain more than 50 percent alcohol.
Hunters and other people handling wild birds, especially waterfowl and shorebirds, should wash hands thoroughly after handling live or dead birds.
Vaccines can prevent seasonal influenza or reduce the severity of a seasonal influenza infection. It helps to get an annual influenza vaccine (flu shot) against seasonal flu, and that vaccine may provide some small amount of protection against the avian or other newer strains in an influenza pandemic; this possibility is still being studied. Once a person becomes sick with an influenza virus, anti-viral medicines can reduce the seriousness of an influenza infection if they are taken within 48 hours of the onset of symptoms. (However, avian influenza H5N1 is resistant to the anti-viral drugs amantadine and rimantadine, so only the neuraminidase inhibitor drugs oseltamivir and zanamivir are currently felt to be effective against that strain.)Like other germ-killing drugs, such as antibiotics, it is essential that a person take all the doses of anti-viral medication that a doctor prescribes for her or him. Stopping a course of antibiotics or anti-virals too soon helps the germs become resistant to the medicine -- in the sick person and everyone else.
What is being done to watch for avian influenza?
Around the world, public health officials, such as the U.S. Centers for Disease Control and Prevention, the World Health Organization (WHO), and the United Nations Food and Agriculture Organization (FAO) are trying to prevent a pandemic by moving quickly to identify and contain influenza outbreaks.
At UC Davis, experts in human and animal health are conducting their own research and education, and are also actively collaborating with colleagues at state agencies, such as the California Department of Health Services; Department of Fish & Game; and Department of Food and Agriculture.
One place UC Davis is watching for dangerous strains of avian influenza is in wild birds. Infected wild birds in Asia could conceivably carry avian influenza to North America, as they migrate east from Asia to North America and then south. Or the virus could be passed through a series of birds from west to east and then north to south. So, in theory, the virus could show up in California in waterfowl or shorebirds that travel along the Pacific Flyway but never were on the Eurasian continent.
At UC Davis, Wildlife Health Center directors Walter Boyce and Jonna Mazet are leading efforts to monitor wild birds. Sampling efforts are under way already in Alaska, under the direction of a UC Davis alumnus, and the team also has begun to sample birds in California. They are concentrating on ducks and geese, and to lesser extent on herons and egrets. They will sample live birds and hunter-killed birds at waterfowl refuges and wetlands. They also will sample sick or dead birds if a disease outbreak occurs.
Wild birds could infect domestic poultry. In an affected flock, experts expect that these warning signs would appear: In chickens and turkeys, a lot of birds would die. Living birds might have coughing or a discharge from the nostrils. They might have a bluish tinge in their combs and wattles, due to lack of oxygen in the blood, and have hemorrhages in the unfeathered skin of the legs. Egg-producing birds would cease laying eggs, and all birds would appear to be severely depressed.
Alternatively, avian influenza might be detected during laboratory analysis of biological samples from a flock submitted by a poultry producer actively participating in the avian influenza surveillance program.
A leader in the program to prevent and detect avian influenza in poultry farms in California is UC Davis associate professor Carol Cardona in the UC Davis School of Veterinary Medicine. Cardona is the sole Cooperative Extension poultry veterinarian in the University of California. She works with large and small poultry producers to develop detection and prevention strategies, and conducts educational workshops for poultry workers on detection and prevention.
In the area of human surveillance and preparedness, UC Davis physicians Warner Hudson and Christian Sandrock have leading roles. At UC Davis Medical Center, they are providing continued medical education training for health practitioners to help them plan, recognize and test for cases of avian influenza in people. Furthermore, they are working with infection-control specialists, local and county public health officers, and state officials to plan, exercise and enhance the Sacramento region's response to a pandemic or other infectious disease disaster. California county and state public health officials are also currently ramping up their pandemic preparedness efforts, as are the CDC and WHO, to strengthen preparedness in this area.
Where is more information about avian influenza online?
-- U.S. Centers for Disease Control and Prevention: http://www.cdc.gov/flu/avian/
-- World Health Organization: http://www.who.int/csr/disease/avian_influenza/en/
-- Food and Agriculture Organization of the United Nations: http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/special_avian.html
-- National Wildlife Health Center of the U.S. Geological Survey:
-- Animal Plant Health Inspection Service of the U.S. Department of Agriculture:
January 5, 2006: UC in Focus spotlights University of California efforts to prevent and prepare for avian influenza
September 27, 2005