The Bird Flu (Avian Influenza)

Avian Influenza in birds:
Bird flu is an infection caused by the H5N1 strain of the avian (bird) influenza (flu) virus. This influenza virus occurs naturally among wild birds. Wild birds worldwide carry the virus in their intestines. Avian influenza is very contagious among domesticated birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them. Cases have been documented of various animals, wild and domesticated, dying of the virus after eating infected birds. “A far wider range of species, including rare and endangered ones, may be affected by highly virulent avian flu than has previously been supposed,” United Nations Environment Program (UNEP) said in a statement in March 2006. It said experts at the Convention on Biological Diversity (CBD) conference in Brazil said “there is growing evidence that the H5N1 virus can infect and harm big cats like leopards and tigers, small cats such as civets and other mammals like martens, weasels, badgers and otters.”

Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated by infected birds. Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.

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.

Human infection with Avian Influenza viruses:
Usually, “avian influenza virus” refers to influenza viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from types of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person. At this time, it is not clear whether cats can pass the virus to humans.

Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.

Studies done in laboratories suggest that some of the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.

Human health risks during the bird flu outbreak:
Of the few avian influenza viruses that have crossed the species barrier to infect humans, the virus has caused the largest number of detected cases of severe disease and death in humans. In the current outbreaks in Asia and Europe more than half of those infected with the virus have died. Since 2003, over 130 human deaths have been contributed to the bird flu. 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 bird flu virus has not yet been defined.

So far, the spread of the bird flu virus from person to person has been limited. Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that the virus one day could be able to infect humans and spread easily from one person to another. Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population. If the virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin.

No one can predict when a pandemic might occur. However, experts from around the world are watching the bird flu virus situation in Asia and Europe very closely and are preparing for the possibility that the virus will begin to spread more easily and widely from person to person.

For More Information:

Centers for Disease Control and Prevention:

World Health Organization (WHO):