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Questions & Answers

Following are some commonly posed questions and answers about pandemics and avian influenza, also known as bird flu.

Source: Department of Health and Human Services

What is avian influenza (bird flu)?

Avian influenza is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide, acting as reservoirs, carry a normally harmless form of influenza viruses in their intestines, and wild birds usually do not get sick from them. Unlike most avian influenza viruses, however, this new strain of H5N1 has caused mortality in more than 80 species of wild birds. Avian influenza can be very contagious among domestic poultry, and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them. 
 
Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The low pathogenic form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100%, often within 48 hours.

Is influenza A (H5N1) virus the only avian influenza virus of concern regarding a pandemic?

Although highly pathogenic H5N1 currently poses a pandemic threat, other avian influenza A subtypes have infected people in recent years. For example, in 1999, H9N2 infections were identified in Hong Kong; in 2003, H7N7 infections occurred in the Netherlands and in 2004, H7N3 infections occurred in Canada. These examples of other avian influenza viruses that have infected humans demonstrate the potential of an influenza virus to evolve into a pandemic strain.

Why are pandemics such dreaded events?

Influenza pandemics are remarkable events that can rapidly infect virtually all countries. Once international spread begins, pandemics are considered unstoppable, because the virus spreads very rapidly by coughing or sneezing. The fact that infected people can share the virus before symptoms appear adds to the risk of international spread via travelers. 
 
The severity of disease and the number of deaths caused by a pandemic virus vary greatly, and cannot be known prior to the emergence of the virus. During past pandemics, attack rates reached 25-35% of the total population. Under the best circumstances, assuming that the new virus causes mild disease, the world could still experience an estimated 2 million to 7.4 million deaths (projected from data obtained during the 1957 pandemic). Projections for a more virulent virus are much higher. The 1918 pandemic, which was uniquely severe, killed at least 40 million people. In the US, the mortality rate of people infected with the virus during that pandemic was around 2.5%. 
 
During a severe pandemic, such as the one that occurred in 1918, there would be large surges in the numbers of people requiring or seeking medical or hospital treatment, temporarily overwhelming health services. High rates of worker absenteeism could also interrupt other essential services, such as law enforcement, transportation, and communications. Because populations will be fully susceptible to a pandemic virus, rates of illness could peak fairly rapidly within a given community. This means that local social and economic disruptions may be temporary. They may, however, be amplified in today's closely interrelated and interdependent systems of trade and commerce.  
 
As all countries are likely to experience emergency conditions during a pandemic, opportunities for inter-country assistance, as seen during natural disasters or localized disease outbreaks, may be curtailed once international spread has begun and governments focus on protecting domestic populations

What are the implications of avian influenza to human health?

 Two main risks for human health from avian influenza are 1) the risk of direct infection when the virus passes from the infected bird to humans, sometimes resulting in severe disease; and 2) the risk that the virus "if given enough opportunities" will change into a form that is highly infectious for humans and spreads easily from person to person.

How does H5N1 virus differ from seasonal influenza viruses that infect humans?

Unlike seasonal influenza, in which infection usually causes only mild respiratory symptoms in most people, H5N1 infection may follow an unusually aggressive clinical course, with rapid deterioration and high fatality. Primary viral pneumonia and multi-organ failure have been common among people who have become ill with H5N1 influenza. 
 
Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 virus has caused the largest number of reported cases of severe disease and death in humans. In the current situation in Asia, Europe, and Africa, more than half of the people infected with the virus have died. Most cases have occurred in previously healthy children and young adults. However, it is possible that the only cases currently being reported are those in the most severely ill people and that the full range of illness caused by the H5N1 virus has not yet been defined.

What are the symptoms of avian influenza in humans?

People infected with the current strand of the avian virus (H5N1) have shown everything from typical human influenza-like symptoms (fever, cough, sore throat, and muscle aches) to pneumonia, severe respiratory diseases, and other life-threatening complications. Symptoms of avian influenza may depend on which specific virus subtype and strain caused the infection.

What age groups are most likely to be affected during an influenza pandemic?

Although scientists cannot predict the specific consequences of an influenza pandemic, it is likely that many age groups would be seriously affected. The greatest risk of hospitalization and death "as seen during the last two pandemics in 1957 and 1968 and during annual influenza" will be infants, the elderly, and those with underlying health conditions. However, in the 1918 pandemic, most deaths occurred in young adults. Few if any people would have immunity to the virus.

How is avian influenza detected in humans?

Avian influenza cannot be diagnosed by symptoms alone. Laboratory testing is required. Avian influenza in people is usually diagnosed by collecting a swab from the nose or throat during the first few days of illness. This swab is then sent to a laboratory, where health professionals will either look for avian influenza virus using a molecular test, or will try to grow the virus. Growing avian influenza viruses should only be done in laboratories with biosafety and biocontainment procedures in place. If it is late in the illness, it may be difficult to find an avian influenza virus directly using these methods. If this is the case, it may still be possible to diagnose avian influenza by looking for evidence of the body's response to the virus. However, this is not always an option, because it requires two blood specimens (one taken during the first few days of illness and another taken some weeks later), and it can take several weeks to verify the results.

Is there a vaccine to protect humans from H5N1 virus?

 There currently is no commercially available vaccine to protect humans against the H5N1 virus that is being detected in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine that will protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way.

Does seasonal influenza vaccine protect against avian influenza infection in people?

 No. Seasonal influenza vaccine does not provide protection against avian influenza.

Why won't the annual flu vaccine protect people against pandemic influenza?

Influenza vaccines provide the best protection against viruses closely related to the vaccine strains. Current annual influenza vaccines include influenza A subtype H3N2 and H1N1 viruses. A vaccine made from these viruses would not provide protection from other influenza A viruses (such as H5N1) that are not closely related to them.

How much time does it take to develop and produce an influenza vaccine?

The influenza vaccine production process is long and complicated. Traditional influenza vaccine production for the U.S. relies on long-standing technology based on chicken eggs. This production technology is labor-intensive and takes up to 9 months from start to finish. 
 
The flu vaccine production process is further complicated by the fact that influenza virus strains continually evolve. Thus, seasonal flu vaccines must be modified each year to match the strains of the virus that are known to be in circulation among humans around the world. As a result of this constant viral evolution, seasonal influenza vaccines cannot be stockpiled year to year. 
 
The appearance of an influenza pandemic virus would likely require creation of a vaccine. Researchers are making and testing possible H5N1 vaccines now.  
 
Large amounts of vaccine cannot be made before knowing exactly which virus will cause the pandemic. It could then take up to 6 months before a vaccine is available and in only limited amounts at first. Research is underway to make vaccines more quickly.

What is the difference between a vaccine and an antiviral?

Vaccines are usually given as a preventive measure. Currently available viral vaccines are usually made from either killed virus or weakened versions of the live virus or pieces of the virus that stimulate an immune response to the virus. When immunized, the body is then poised to fight or prevent infection more effectively.  
 
Antivirals are drugs that may be given to help prevent viral infections or to treat people who have been infected by a virus. When given to treat people who have been infected, antiviral medications may help limit the impact of some symptoms and reduce the potential for serious complications, especially for people who are in high risk groups.

How is avian influenza in humans treated?

Supportive care is important, as it is for annual influenza. Laboratory studies suggest that two prescription medicines approved for human influenza viruses, Tamiflu® and Relenza®, may work in treating avian influenza infection in humans. Clinical trials involving people with H5N1 are needed to see how effective they will actually be. In addition, influenza viruses can sometimes become resistant to these drugs, so these medications may not always work.

What kinds of wild birds primarily carry avian influenza?

Most avian influenza viruses have been isolated from wild waterfowl (ducks, geese, and swans) and shorebirds (wading birds), gulls, and terns. With rare exceptions, the thousands of flu isolates found in wild birds have been low pathogenic avian influenza and have rarely caused signs of illness in wild birds. The occurrence of avian influenza in wild ducks in North America reaches its height in late summer and early fall. At other times of the year, infection rates are usually less than 1 percent. In shorebirds, infection rates are highest during the spring migration, although in comparison with waterfowl, their infection rates are much lower.

Can migratory birds bring highly pathogenic avian influenza (HPAI) H5N1 to North America?

Migratory birds usually travel thousands of miles over the same routes in their annual migrations. In the Northern Hemisphere, birds begin moving south during August and September of each year. North American migratory birds that spend the winter in Asia may come into contact with potentially infected domestic or wild birds during the winter months.  
 
In spring, migratory birds will migrate north to their breeding grounds in eastern Russia, Alaska, and Canada. Migratory birds infected with the highly pathogenic avian influenza (HPAI) H5N1 returning from Asia could potentially interact with other North American wild birds as they commingle on the breeding grounds.  
 
Bird migration is only one possible route of introduction of HPAI H5N1 into North America. Illegal smuggling of birds and poultry products, travel by infected people, or people traveling with virus-contaminated articles are more direct, and possibly more likely, means of introducing the new strain of HPAI H5N1 virus into the United States.

Is there a risk for becoming infected with avian influenza by eating poultry?

There is no evidence that properly cooked poultry can be a source of infection for avian influenza viruses. Furthermore, the likelihood of infected poultry entering the U.S. food supply is extremely low due to import restrictions, extensive avian influenza testing programs, and federal inspection programs. Even if it did, properly prepared and cooked poultry is safe to eat. Cooking poultry to an internal temperature of 165°F kills the avian influenza virus as it does other bacteria and viruses. While most human illnesses have resulted from direct contact with sick or dead birds, a small number have resulted from eating raw poultry or poultry products so proper cooking is important if there is a concern that the avian influenza virus might be present. The U.S. Department of Agriculture (USDA) advises that cooking poultry to the proper temperature and preventing cross-contamination between raw and cooked food is the key to food safety. Consumers are reminded to:

  • Wash hands with warm water and soap for at least 20 seconds before and after handling food.
  • Prevent cross-contamination by keeping raw poultry, meat, and fish and their juices away from other foods.
  • After cutting raw meat, wash cutting board, knife, and countertops with hot, soapy water.
  • Sanitize cutting boards by using a solution of 1 teaspoon chlorine bleach in 1 quart of water; and
  • Use a food thermometer to ensure poultry has reached the safe internal temperature of at least 165°F to kill food-borne germs that might be present, including the avian influenza virus.

Is it safe to eat raw eggs?

Eggs from infected poultry could also be contaminated with the virus and therefore care should be taken in handling eggs or raw egg products. Commercial mayonnaise, dressings, and sauces that contain pasteurized eggs are safe to eat. The Food and Drug Administration (FDA) discourages the consumption of eggs that have not been adequately cooked. FDA advises consumers to avoid eating or tasting foods that may contain raw or lightly cooked eggs, such as:

  • raw batter, filling, or cookie dough made with raw eggs;
  • eggnog and other egg-fortified beverages that are not thoroughly cooked; and
  • homemade and fresh-made dressings and sauces made with raw eggs such as Caesar salad dressing, bearnaise sauce, Hollandaise sauce, aioli sauce, mayonnaise; homemade ice cream; mousse; meringue; or tiramisu.

How would pandemic flu affect communities and businesses?

If a severe influenza pandemic occurs, many people could become sick at the same time and would be unable to go to work. Many would stay at home to care for sick family members. Schools and businesses might close to try to prevent disease spread. Large group gatherings might be canceled. Public transportation might be scarce. These are examples of challenges that local communities, schools, civic organizations, and businesses will have to work together on to plan for a pandemic response.

What precautions should I take if I live or visit in an area affected by H5N1 bird flu?

  • Avoid contact with live birds, chickens, ducks, turkeys, geese, and their feces, feathers, and pens if at all possible.Children, in particular, should be warned and precautions enforced.
  • Pet birds should not be kept.
  • If preparing poultry, cook it well done before eating.
  • Avoid cross contamination of other foods by use of separate kitchen utensils and surfaces exposed to raw poultry.
  • Wash hands with soap and water after any poultry contact.
  • Be sure, if possible, that poultry does not live near your housing area.
  • Do not transport live or dead poultry even if it appears to be healthy.
  • Avoid poultry products from areas of infected birds.
  • If you must travel to infected areas and work directly with infected birds, poultry or humans, hand washing and shoe and clothing cleaning should be an immediate priority.
  • Be sure to wear gloves, a special N-95 mask, goggles, and a disposable gown if you must be in contact with the birds/poultry in enclosed environments where aerosolization of the small virus particles may occur.
  • Observe yourself for the development of any respiratory or gastrointestinal symptoms after the visit and check your temperature for a week afterwards, and contact a physician if you have any questions.

What changes are needed for H5N1 or another avian influenza virus to cause a pandemic?

Three conditions must be met for a pandemic to start: 1) a new influenza virus subtype must emerge for which there is little or no human immunity; 2) it must infect humans and cause illness; and 3) it must spread easily and sustainably (continue without interruption) among humans.

The H5N1 virus in Asia, Europe, and Africa meets the first two conditions: it is a new virus for humans (H5N1 viruses have never circulated widely among people), and it has infected a growing number of people, killing over half of those known to have been infected. However, the third condition, the establishment of efficient and sustained human-to-human transmission of the virus, has not occurred. For this to take place, the H5N1 virus would need to improve its transmissibility among humans.

Three conditions must be met for a pandemic to start: 1) a new influenza virus subtype must emerge for which there is little or no human immunity; 2) it must infect humans and cause illness; and 3) it must spread easily and sustainably (continue without interruption) among humans.

The H5N1 virus in Asia, Europe, and Africa meets the first two conditions: it is a new virus for humans (H5N1 viruses have never circulated widely among people), and it has infected a growing number of people, killing over half of those known to have been infected. However, the third condition, the establishment of efficient and sustained human-to-human transmission of the virus, has not occurred. For this to take place, the H5N1 virus would need to improve its transmissibility among humans.

What precautions can hunters take to reduce the risk for infection from avian influenza when hunting birds in the United States? 

Hunters should follow routine precautions when handling game, including wild birds. The U.S. Geological Survey’s National Wildlife Health Center recommends that hunters:

  • do not handle or eat sick game;
  • wear rubber or disposable latex gloves while handling and cleaning game, wash hands with soap and water (or with alcohol-based hand products if the hands are not visibly soiled), and thoroughly clean knives, equipment, and surfaces that come in contact with game;
  • do not eat, drink, or smoke while handling animals;
  • disinfect tools, gloves, and materials that come into contact with killed birds;
  • place uncooked game in a plastic bag or container for transport; and
  • cook all game thoroughly; cooking to 165 degrees Fahrenheit kills the virus.

Is there a risk in handling feather products that come from countries experiencing outbreaks of avian influenza A (H5N1)?

The U.S. government has determined that there is a risk to handling feather products from countries experiencing outbreaks of H5N1 influenza.  
 
There is currently a ban on the importation of birds and bird products from H5N1-affected countries in Africa, Asia, and Europe. The regulation states that no person may import or attempt to import any birds (Class Aves), whether dead or alive, or any products derived from birds (including hatching eggs), from the specied countries. This prohibition does not apply to any person who imports or attempts to import products derived from birds if, as determined by federal officials, such products have been properly processed to render them noninfectious so that they pose no risk of transmitting or carrying H5Nl and which comply with the U.S. Department of Agriculture (USDA) requirements. Therefore, feathers from these countries are banned unless they have been processed to render them noninfectious. Additional information about the import ban is available on the USDA website.  

Avian Influenza Infection in Animals

Is there a risk to importing pet birds that come from countries experiencing outbreaks of avian influenza A (H5N1)?

 The U.S. government has determined that there is a risk to importing pet birds from countries experiencing outbreaks of H5N1 influenza. CDC and USDA have both taken action to ban the importation of birds from areas where H5N1 has been documented. There is currently a ban on the importation of birds and bird products from H5N1-affected countries in Africa, Asia, and Europe. The regulation states that no person may import or attempt to import any birds (Class Aves), whether dead or alive, or any products derived from birds (including hatching eggs), from the specified countries.

What animals can be infected with avian influenza A (H5N1) viruses? 

In addition to humans and birds, we know that pigs, tigers, leopards, ferrets, and domestic cats can be infected with avian influenza A (H5N1) viruses. In addition, in early March 2006, Germany reported H5N1 infection in a stone marten (a weasel-like mammal). The avian influenza A (H5N1) virus that emerged in Asia in 2003 is evolving and it's possible that other mammals may be susceptible to infection as well. CDC is working closely with domestic and international partners to continually monitor this situation and will provide additional information to the public as it becomes available.

Can domestic cats be infected with avian influenza viruses? 

While domestic cats are not usually susceptible to influenza type A infection, it is known that they can become infected and die (both experimentally and naturally) with avian influenza A (H5N1) viruses and, in a laboratory/research setting can spread the virus to other cats. It is not known whether domestic cats can spread the virus to other domestic cats under natural conditions.

How do cats become infected with avian influenza A (H5N1) viruses?

All of the cases of influenza A (H5N1) infection in domestic cats reported to date have been associated with H5N1 outbreaks among domestic poultry or wild birds and are thought to have occurred by the cat eating raw infected birds.

How commonly have cats been infected with avian influenza A (H5N1) viruses?

During the avian influenza A (H5N1) outbreak that occurred from 2003 to 2004 in Asia, there were only several unofficial reports of fatal infections in domestic cats. Studies carried out in the Netherlands and published in 2004 showed that housecats could be infected with avian influenza A (H5N1) and could spread the virus to other housecats. In these experiments, the cats became sick after direct inoculation of virus isolated from a fatal human case, and following the feeding of infected raw chicken. In February 2006, Germany reported that a domestic cat had died from influenza A (H5N1) infection. That cat lived in the northern island of Ruegen, where more than 100 wild birds are believed to have died of the disease. The cat probably got sick by eating an infected bird.

What about infection in large cats, like tigers?

Large cats kept in captivity have been diagnosed with avian influenza as well. In December 2003, two tigers and two leopards that were fed fresh chicken carcasses from a local slaughterhouse died at a zoo in Thailand. An investigation identified avian influenza A (H5N1) in tissue samples. In February and March 2004, the virus was detected in a clouded leopard and white tiger, respectively, both of which died in a zoo near Bangkok. In October 2004, 147 of 441 captive tigers in a zoo in Thailand died or were euthanatized as a result of infection after being fed fresh chicken carcasses. The cats are thought to have gotten sick from eating infected raw meat. Results of a subsequent investigation suggested that at least some tiger-to-tiger transmission occurred in that facility.

Can cats spread H5N1 to people?

There is no evidence to date that cats can spread H5N1 to humans. No cases of avian influenza in humans have been linked to exposure to sick cats, and no outbreaks among populations of cats have been reported. All of the influenza A (H5N1) infections in cats reported to date appear to have been associated with outbreaks in domestic or wild birds and acquired through ingestion of raw meat from an infected bird.

What is the risk to humans or other species from cats infected with avian influenza H5N1 virus?

There is no evidence to date that cats can spread H5N1 to humans. No cases of avian influenza in humans have been linked to exposure to sick cats, and no outbreaks among populations of cats have been reported. All of the influenza A (H5N1) infections in cats reported to date appear to have been associated with outbreaks in domestic or wild birds and acquired through ingestion of raw infected meat.

What is the current risk that a cat in the United States will become infected with influenza A (H5N1)? 

As long as there is no influenza A (H5N1) in the United States, there is no risk of a U.S. cat becoming infected with this disease. The virus circulating in Asia, Europe and Africa has not yet entered the United States. CDC is working closely with domestic and international partners to continually monitor this situation and will provide additional information to the public as it becomes available.

If avian influenza A (H5N1) is identified in the United States, how can I protect my cat?

As long as there is no H5N1 influenza in the United States, at this time there is no risk of a U.S. cat becoming infected with this disease. In Europe, however, where H5N1 has been reported in wild birds, poultry, several cats, and a stone marten (a member of the weasel family), the European Center for Disease Prevention and Control has issued preliminary recommendations for cat owners living in H5N1-affected areas. Additionally, the Food and Agriculture Organization has produced guidance for areas where H5N1 HPAI has been diagnosed or is suspected in poultry or wild birds.

Can dogs be infected with avian influenza?

While dogs are not usually susceptible to avian influenza viruses, the avian influenza A (H5N1) virus that emerged in Asia in 2003 has been documented to infect other carnivore species (e.g. cats, tigers, leopards, stone martens). This has raised concern that this strain of avian influenza A (H5N1) virus may be capable of infecting dogs. An unpublished study carried out in 2005 by the National Institute of Animal Health in Bangkok indicated that dogs could be infected with the virus, but no associated disease was detected. This limited information is not enough to determine definitively whether dogs are susceptible to the virus. CDC is coordinating with USDA, veterinary associations, and other partners domestically and internationally on this issue and will provide additional information to the public as it becomes available.

How would dogs be infected with avian influenza A (H5N1)?

There is not enough information available about avian influenza A (H5N1) infection in dogs to know how infection would occur. Affected domestic cats in Europe appear to have become infected by feeding upon raw infected poultry or wild birds. If dogs are susceptible to avian influenza A (H5N1), infection may be by the same route.

What is the current risk that a dog in the United States will become infected with avian influenza A (H5N1)?

As long as there is no influenza A (H5N1) in the United States, there is no risk of a U.S. dog becoming infected with this disease. The virus circulating in Asia, Europe and Africa has not yet entered the United States. CDC is working closely with domestic and international partners to continually monitor this situation and will provide additional information to the public as it becomes available.

 

 

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