Bird flu is an infectious disease of birds caused by the influenza virus. Domestic poultry are highly vulnerable. In its highly pathogenic form, the disease is extremely contagious and rapidly fatal. Mortality in poultry can approach 100% and they can die the same day symptoms appear.Some birds, such as waterfowl, are more resistant to disease.Outbreaks are often difficult to control. The disease can spread quickly in a flock and from farm to farm through droppings and contaminated
material.
Avian influenza is flu infection in birds. The disease is of concern to humans, who have no immunity against it. The virus that causes this infection in birds can mutate (change) to easily infect humans. Such mutation can start a deadly worldwide epidemic.Farmers and other people working with poultry, as well as travelers visiting affected countries, have a higher risk for getting the bird flu. Handling an infected bird can cause infection. People who eat raw or undercooked poultry meat are also at an increased risk for avian influenza.Healthcare workers and household contacts of patients with avian influenza may also be at an increased risk of the bird flu.
Avian flu (also "bird flu", "avian influenza", "bird influenza"), means "flu from viruses adapted to birds", but is sometimes mistakenly used to refer to both other flu subsets (such as H5N1 flu) or the viruses that cause them (such as H5N1).Avian flu is caused by a form of influenza virus that usually only infects birds and sometimes infects pigs. The few people who have become sick or died from the bird flu had direct contact with infected birds.Like the flu that affects humans, there are lots of different strains (varieties) of bird flu.The strain of bird flu that has infected people in Asia and the Middle East recently is called H5N1. H5N1 is one of the strains that are dangerous to birds.The people who became infected with the H5N1 strain of avian flu caught it directly from birds. H5N1 cannot be spread from person to person.
This raised considerable alarm. Never before in recorded history has highly pathogenic bird flu been so widespread and persistent. Never before have so many outbreaks occurred at the same time in several countries. Never before have so many people been infected directly and become ill.The clinical spectrum of influenza A (H5N1) in humans is based on descriptions of hospitalized patients. The frequencies of milder illnesses, subclinical infections, and atypical presentations (e.g., encephalopathy and gastroenteritis) have not been determined, but case reports indicate that each occurs. Most patients have been previously healthy young children or adults.
The incubation period of avian influenza A (H5N1) may be longer than for other known human influenzas. In 1997, most cases occurred within two to four days after exposure13; recent reports15,16 indicate similar intervals but with ranges of up to eight days . The case-to-case intervals in household clusters have generally been 2 to 5 days, but the upper limit has been 8 to 17 days, possibly owing to unrecognized exposure to infected animals or environmental sources.This is a severe disease. It is not typical flu. It starts out with pneumonia, whereas in many cases flu may develop into pneumonia but most of the time it doesn't,” Monto said. It also moves throughout the body's organs and becomes what's known as a systemic infection.
Every few years, one of these flu bugs makes a major genetic leap and becomes a form of flu no human immune system has ever encountered and for which there are no known vaccines.The virus the world flu experts are watching right now is called H5N1 influenza, known informally as avian flu or bird flu. If the flu bugs we see in a regular year are handguns, H5N1 is an AK-47.H5N1 has killed about 60 percent to 70 percent of those who've been infected in Asia , and birds carrying the virus have recently been found in Romania and Turkey , showing it's moving west.
The Food and Drug Administration has approved the first bird flu vaccine in the United States. The bird flu vaccine is designed to protect against the current form of the H5N1 bird flu virus, should it develop the ability to spread efficiently among humans and create a pandemic outbreak. This bird flu vaccine could be used early in such an outbreak to provide limited protection until another vaccine — designed to protect against the specific form causing the outbreak — is developed and produced.
Viruses often change (mutate). They may then spread more easily among animals and humans. They can also become more deadly. The strain of influenza that is now common in birds in Asia could change into a flu that spreads more easily to humans. National and world health organizations worry that a mutated bird flu virus could cause a world-wide epidemic (pandemic). Many people have at least some immunity to human viruses, which means their body can more easily fight the virus. A pandemic happens when there are worldwide epidemics of flu caused by a new flu virus to which people have little or no immunity.
PAHO officials emphasized today that no one can predict if or when avian influenza will reach the Americas, but the risk exists. “The key to fighting H5N1 is to make sure we have effective surveillance, with quick reporting, and to be prepared to respond to any outbreak, if and when it occurs,” said Albino Belotto, head of PAHO’s Veterinary Public Health program.
PAHO and the World Health Organization have warned that the international spread of H5N1 in birds increases the chances that the virus could mutate to become easily transmissible from person to person, which could spark a global pandemic.
While many health experts see the H5N1 bird flu virus as a likely cause for an influenza pandemic, another influenza virus could just as likely mutate into a global killer, U.S. health experts said on Tuesday.
"You can not accurately predict if and when a given virus will become a pandemic virus," said Anthony Fauci, head of the U.S. National Institute of Allergy and Infectious Diseases.
Fauci said too little is known about exactly how and when a virus will mutate. Focusing too much on one suspect -- even a very likely suspect such as H5N1 -- may be a mistake.
"We should not ... forget the fact that historically pandemics have evolved. We should be building up the knowledge base and expanding the capabilities of making vaccines," he said in a telephone interview.
Fauci and colleagues, writing in a commentary in the Journal of the American Medical Association, said pandemic prevention strategies must based on "expecting the unexpected and being capable of reacting accordingly."
They recommend companies expand their research on vaccine design, develop new classes of drugs and improve tests to diagnose influenza.
The H5N1 avian influenza virus that is now killing birds in countries from Indonesia to Nigeria rarely infects people.
But many believe if it mutates in just the wrong way, it could start passing easily from one person to another and would sweep the globe, killing millions.
Companies and governments are working feverishly to prepare for a pandemic by developing vaccines and stockpiling drugs to treat viruses.
But focusing too much on just one viral suspect may leave the world vulnerable in the event that another virus causes a deadly flu pandemic.
"The ability of these types of viruses to ultimately spread from birds to humans is a very complex process involving multiple genetic evolutions. It's a complicated issue that is very difficult to predict," Fauci said.
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