Bird Flu: Disease takes off around the world, remains primarily an avian threat - DVM
News Center
DVM Featuring Information from:


Bird Flu: Disease takes off around the world, remains primarily an avian threat


Pathologic examination of humans who have died of disease due to H5N1 demonstrates similar pathologic changes as to what is seen in birds experimentally infected with H5N1. Also, experimental infection of cats yields the same clinical course and pathologic picture.

E for eradication

Outbreaks of HPAI are usually approached through a stamping out policy. The virus spreads readily from bird to bird through any kind of body secretion so an entire house will be affected in short order. Poultry mortality with strains of HPAI approaches 100 percent. It is important to eliminate all infected birds and their contacts in order to keep the disease from spreading.

A vaccine exists for avian influenza and is used in some areas to help with control. Unfortunately, a vaccinated bird could still be infected with the virulent form of HPAI, might not appear sick, but could still shed virus. Consequently, any poultry vaccination campaign needs to be accompanied by strict surveillance and continued biosecurity.

F is for the future

Most scientists believe that it will be difficult to avoid an incursion of the H5N1 virus into North America. Either through illegal movement of poultry or through migratory birds, the virus will undoubtedly hitchhike a ride to enter our 50 states. Within the United States, we have well-developed mechanisms to respond to outbreaks in poultry, and it is likely that these response plans would be implemented immediately and help confine the outbreak.

The greater concern is about the occurrence of a pandemic (that is, an influenza virus that causes disease in people on multiple continents). There is a possibility that the bird flu virus may mutate so that it becomes capable of human-to-human spread. Specifically, it would have to mutate in such a way that the virus could use receptors that are present in the upper respiratory tract of humans (as the human influenza A viruses do currently). It is not possible to quantify such a risk, and estimates vary widely.

If the virus does mutate to allow for human-to-human spread, control is far less certain. In the recent ABC made-for-TV movie, "Fatal Contact: Bird Flu in America", this mutation and spread scenario plays out. The first new cases occur in China, and human-to-human transmission is recognized as reality. When an alarmed American epidemiologist asks the Chinese physician if it is too late for containment, the physician responds, "What do you mean, we lost our chances at containment? We never had any chance of containment." This statement is chilling but accurate. The extensive nature of commerce and international travel dictates there will be rapid and global spread.

G means global

The H5N1 strain of avian influenza has now been diagnosed in birds in at least 50 countries of the world. In each new focus, there is an attempt to control the disease through slaughtering of infected poultry. There is little doubt that any country will be able to escape incursion of this avian virus.

To date, there have been more than 200 laboratory-confirmed human infections in nine countries. More than half of the infected people have died. If there is a mutation to allow for easy transmission among people, every country in the world will definitely be affected.

Hope, with a capital H

The good news is that as a result of aggressive campaigns to destroy affected poultry and undertake effective vaccination campaigns, Southeast Asia, the place where the disease first surfaced, is now reporting that large areas are free of the scourge. Also, recent reports that birds returning to Europe after a winter in Africa are not bringing any virus back with them brings hope that Europe does not face massive reinfection through migratory birds. There is a general acknowledgment that wild birds are not playing a major role in spread and that if illegal poultry movement is better controlled, spread can be minimized further.

Veterinarians also should take pride in international efforts to control this disease. Experts from human medicine, veterinary medicine and the wildlife community, representing multiple countries, all came together in a global and team-oriented approach. This template, with its well-integrated veterinary expertise, will serve us well for the next disease threat. Based on recent history of emerging disease threats, e.g., BSE, Ebola, SARS, the next threat will probably be a zoonotic disease. In each of these cases as well as with avian influenza, a problem surfaced first in animal populations before spreading to humans. There is growing recognition that disease in animals can serve as a harbinger of human infection.

Avian flu in birds might just be the canary in the coal mine and our effective response to the danger hopefully has kept and will continue to keep that threat from spreading into a major human pandemic. Veterinarians provide an absolutely vital link to the health of all populations.

Dr. Brown is professor and coordinator of international activities for the University of Georgia's College of Veterinary Medicine.


Source: DVM360 MAGAZINE,
Click here