(Photo courtesy of U. S. Department of Agriculture)
Will bird flu be the next human pandemic? In a few words, the answer is simply, “No one knows yet,” says Dr. Tim Moody, Public Health Officer, Whitman County.
That’s because the specific virus causing what we call bird flu, or avian influenza, must undergo significant, specific mutations to gain the ability to infect humans easily as well as move from human to human. When and if that will happen is unknown.
Scientists and public health officials are watching closely for any clue that it may be happening. So far, the virus is not showing telltale signs it is moving toward such mutations.
Wild birds, especially waterfowl and shorebirds, have been known for many years to be the natural host for all known subtypes of the influenza A viruses, including the H5N1 subtype. Typically, wild birds do not get sick when infected with these viruses. Once in a while however, an influenza subtype circulates among birds and is especially deadly. That’s the case with the current bird flu virus known more properly as the Eurasian lineage strain of H5N1 influenza A and the one heading up media stories.
High vs. low pathogenic
The descriptive distinction is important and very confusing for most people. The media is built on brevity and cuts the virus description down to just “H5N1,” or “bird flu.” Most importantly, the public should realize there are two forms of the avian influenza H5N1 virus. One type does relatively little and is referred to as “low pathogenic H5N1.” This form is common in waterfowl and causes little disease or death. Low pathogenic H5N1 virus may be detected in the U.S. with the increased surveillance underway, as it was in Canada last fall. Its detection is not a cause for alarm and does not mean Eurasian H5N1 is following.
Eurasian H5N1 is the “highly pathogenic” form and has the media and public’s attention in the wake of poultry farm depopulations in some countries. It causes a high percentage of infected birds to die. Management entails killing off the remaining birds to stop the disease spread.
127 deaths since 2003
Eurasian H5N1 has also caused 127 human deaths total in 10 countries since 2003 and sickened about twice that many. By any measure, this virus is not a major human health concern at this time but puts a premium on reasonable preparation, close monitoring, and surveillance like that underway currently.
Close to poultry
It is also important to understand why people have become infected and died. In Southeast Asia and China, many people live in close proximity to domestic poultry. Many in fact cohabitate with their fowl, so the total number of virus particles they are exposed to is tremendous.
If this disease remains almost exclusively in birds, it is unlikely that many people worldwide will ever experience this high level of exposure or viral load. But some people in less developed parts of the world have gotten sick and about 50 percent of those (127) have died.
Human to human transmission
There has not been any sustained human to human transmission of Eurasian H5N1 influenza. So far, the spread of H5N1 virus from person to person has been rare, inefficient (not easily transmitted) and unsustained. This includes a recent cluster of cases in Indonesia in which eight members of one family have contracted Eurasian H5N1 and seven have died. Complete genetic analyses show there are no changes in the virus in Indonesia compared with other H5N1 viruses isolated recently. This evidence does not indicate or suggest that the virus has become more virulent or that a pandemic is imminent.
Quickly spread in birds
Surprisingly, Eurasian H5N1 has spread somewhat quickly among birds. In a very short time, it moved from Southeast Asia to Northern Europe. Soon, North American bird species will mingle with those from Asia, and could bring this form of the virus onto the continent and into the U.S.
Hoping for the best, but preparing for the worst, federal, state and local public health and safety officials are preparing to deal with Eurasian H5N1 influenza A should key mutations occur that might lead to a human influenza pandemic.
Whitman County and WSU
Beginning last fall, representatives from Whitman County law enforcement agencies, fire services, hospitals, schools, Washington State University, the Red Cross, and public health have been developing plans to mitigate the impact of a pandemic influenza on city and county residents should it occur and regardless of what virus type causes it.
A key planning component is to keep citizens informed and prepared, which is the reason for this article. Knowledge and proper planning will be the best resource in the event of any major health crisis, not just so-called “bird flu.” That is why planning is important and some day it may be vital.
To stay informed, look for additional columns in the future and also visit the Centers for Disease Control and Prevention webpage on Avian flu: http://www.cdc.gov/flu/avian/gen-info/facts.htm and visit the Whitman County Public Health website at:
Look for future articles on:
* Differences between seasonal, pandemic and avian influenza.
* Use of vaccination and anti-viral medication to control pandemic influenza.
* Individual and population-based approaches to prevent the spread of influenza.