Bird flu or avian flu, as its name implies, is primarily a disease of birds. It is caused by the influenza A virus, which was first identified in Italy more than 100 years ago. The virus has at least 15 subtypes that can infect birds.
In birds, the flu virus is transmitted from individual to individual through contact with saliva, nasal secretions or feces. Among domesticated birds and poultry, the virus causes widespread disease and death. In fact, epidemics of avian influenza that kill millions of domestic poultry occur periodically. Among wild birds, however, the disease usually causes only minor or no symptoms, but wild birds play an important role in spreading the disease to domestic fowls.
Bird flu started to affect humans only a few years ago. In May 1997, in Hong Kong, the first case of the disease in humans was reported following a widespread epidemic of bird flu among chickens. Apparently, a strain of the virus (H5N1) mutated and started to infect humans. By the time the outbreak was contained in early 1998 — through the mass destruction of 1.5 million chickens, the thorough cleansing of the markets and chicken stalls, etc. — a total of 18 human cases that resulted in six deaths had been recorded.
There have been other outbreaks of bird flu in Asia since, but most had been caused by the less lethal H5N2 and other benign strains of the avian influenza type A virus. In any case, very few human cases and deaths from the disease have been reported — till this current outbreak.
The ongoing worldwide outbreak of avian influenza, which began in Southeast Asia in mid-2003, is the largest and most severe on record. Its causative agent is a highly pathogenic and especially tenacious strain of the influenza A virus called H5N1. To date, the number of chickens that have died — including those that were intentionally culled to prevent the spread of the disease — is in the hundreds of millions.
The current bird flu epidemic has affected Indonesia, Vietnam, Cambodia, China, Thailand, Laos, Republic of Korea, Japan, Malaysia, Russia, Kazakhstan, Mongolia, Turkey and Romania. The last two countries are the most recent additions to the list, having confirmed the existence of bird flu in their domestic poultry only in October 2005.
Japan, Republic of Korea, and Malaysia have announced control of their poultry outbreaks and are now considered free of the disease, but in the other affected areas, outbreaks continue in varying degrees of severity.
In terms of human toll, as of October 20 this year, a total of 188 human cases of avian flu have been recorded worldwide. Of these, 61 have resulted in deaths. Two-thirds of these deaths occurred in Vietnam, the rest occurred in Thailand, Cambodia and Indonesia.
In humans, the main route of infection with bird flu is via direct contact with infected poultry, or surfaces and objects contaminated by their droppings. The risk of the virus infecting humans is highest during slaughter, de-feathering, butchering, and preparation of poultry for cooking. There is no evidence that properly cooked poultry or poultry products can be a source of infection — and this should answer your first question.
As long as the mode of transmission of the avian flu to humans stays as is, i.e., bird to human, the disease will not become widespread among humans. An infection has to be transmitted from person-to-person for it to reach epidemic and pandemic proportions.
Is there a real threat of an avian flu pandemic? Most experts say there is. In fact, some say a pandemic is imminent. The World Health Organization (WHO) assesses the threat of a pandemic at phase 3: A virus is causing infections, but does not spread easily from person to person.
Actually, a flu pandemic caused by a virus that primarily affects animals is not unprecedented. In 1918 to 1919, the world was ravaged by the Spanish flu, a disease believed to have been caused by a mutant virus that initially jumped from animal to man before it became capable of person-to-person transmission. Estimates of human fatalities caused by the Spanish flu pandemic ranged from 20-100 million.
A scenario similar to that seen in 1918 seems to be unfolding at present. Fortunately, to date, there has been only one confirmed case of person-to-person transmission of bird flu. This occurred in Thailand where a mother got sick and eventually died from avian influenza after acquiring the virus from her sick child. Luckily, this person-to-person transmission did not result in a sustained transmission of the disease.
There is presently an international effort, spearheaded by the World Health Organization (WHO), to prepare for a worst-case scenario for avian flu. The WHO has urged drug companies to speed up vaccine production and to increase production of antiviral drugs. It has also operationalized a worldwide surveillance system for the disease.
