A Facebook conversation prompts me to examine the current situation with the A type H5N1 influenza virus, known as “bird flu” or “avian flu”. Birds suffer from several types of influenza, however, and most are not contagious for humans. The terms “bird flu” and “avian flu” are, thus, very non-specific.
A)H5N1 is the influenza virus that was discovered in Scotland, in birds, in 1959. It was first seen in humans in 1997, after 1996-97 outbreaks in birds in China and Hong Kong.
To date, the World Health Organization is reporting 397 cases, of which 249 were fatalities. 63% of the reported cases were fatal.
Indonesia has had the most cases and one of the highest death rates at 81%. Vietnam runs second, and its death rate is 49%. 12 countries in Asia and three in Africa have reported human cases of A)H5N1.
The number of cases peaked in 2006 and dropped in both 2007 and 2008. Several notions occur when examining the geographical spread of H5N1 in humans and in birds.
There are large geographical areas where no avian infection have been reported separating areas where they have. This suggests that the countries involved lack the capability to discover infections, or are not reporting them. Given the dictatorial nature of most of the governments in the “blank” areas, one would lean towards non-reporting as a reason.
You will also note the odd distribution in China. The populous and wealthy coast has no cases. China lied repeatedly about SARS and it is very possible that they are lying about H5N1.
There have been several clusters of H5N1 that suggest human to human transmission [ H2H ]. One such, from Indonesia, involves an extended family that spent time with and cared for a dying relative in a small room. Close, intimate contact may transmit the disease, however that are far more intimate contacts that did not contract H5N1 so it may just be one variant that is contagious.
To date, the overwhelming number of cases involve people in rural areas who have close, daily contact with poultry. The handling of sick birds, the slaughter and preparation of sick birds and the common practice of keeping poultry in living quarters all provide ample opportunity for infections. Since women and children usually farm the poultry, they are the primary population to become sick.
It has only been in the last year to two that laboratories in East Asia were certified to be able to test for H5N1. Prior to that, the samples had to be sent to WHO labs or to labs in the West with testing capability. News reports based upon local tests from several years ago are not reliable indicators for the spread of H5N1.
Progress on a vaccine is being made. The virus is continually changing and more than one variant is responsible for human illnesses. Nine “clades” have been isolated, 0-9, and sub-clades and variants within the sub-clades. Clades 1, 2.1, 2.2 and 2.234 have caused human cases.
WHO is building a stockpile of H5N1 vaccines, and 9 different versions were approved as of September 2008. More were pending but the genetic properties of H5N1 have been varying enough that many variants do not have vaccine programs proposed for them as yet.
Because of the small number of actual cases, the WHO does not have good data on the effects of any vaccine in a human population. Animal studies suggest that vaccines can be effective, and that their ability to produce antibodies can be safely improved upon with vaccine additives. Without knowing which H5N1 clade, sub-clade or variant will produce the predicted pandemic, production of vaccines is driven more by the variant appearing in a given region than a world-wide threat.
That said, the WHO recognizes the difficulty of delivering vaccines to rural, remote regions. Some of the cases in Indonesia could only be reached on donkey back, for example. The polio outbreak in 2006 and 2007 that was caused by Islamic teachers in Nigeria refusing to allow vaccinations to take place suggests yet another reason that WHO plans for the Third World will have to be vastly different than those for the West.
There are at least four separate versions of H5N1 that are producing illness in humans. In all less than 400 total cases have been seen. Many of the countries in the region affected by outbreaks in birds have governments that control the news and are not forthcoming about many of the events in their nations.
I continue to believe that there is no evidence that H5N1 will produce the next influenza pandemic. The Spanish Flu version, H1N1, is in circulation and has equally as much of a chance, perhaps more since tens of thousands more cases of H1N1 happen in humans every year.
I also continue to believe that there is no evidence that the next influenza pandemic will be any deadlier than the last two. We have good data on two, and poor data on a third, and that suggests to me that we do not have enough information to make any assumptions about future pandemics.
You may find all my work on H5N1 at this category link: Avian Flu.
