Highly Pathogenic Avian Influenza
The flu should always be taken seriously.
The data suggests that we have already passed through the period of widespread influenza this winter. Only sporadic cases are being reported in New York State and nationally the picture is similar. I hope that this will not lull us into a sense of security and head us off from getting flu shots next year.
For even in "good" years when flu is not widespread, as John Barry points out in The Great Influenza (Viking), this disease kills 36,000 people worldwide. His fine book is about the 1918 flu pandemic which he rightly calls in his subtitle the Deadliest Plague in History. That flu killed 50 to 100 million people, among them more than one out of twelve young adults in this country.
Flu is in the news now because of the outbreak of highly pathogenic avian influenza (HPAI) among poultry in the Orient and now in at least one case in this country as well.
The disease was first reported in poultry in South Korea in mid-December but it was soon identified in Vietnam, Japan, Taiwan, Thailand, Cambodia, Hong Kong, Laos, Pakistan, China and Indonesia. A case has also been reported in British Columbia and we too are not immune: in early February an outbreak in Delaware was confirmed.
To control the spread of HPAF among poultry, millions of chickens and ducks have been destroyed including that flock of 12,000 birds in Delaware.
Now human cases have begun to be reported, so far restricted to Thailand and Vietnam. The severity of this strain is indicated by the fact that of the 32 cases hospitalized 22 died.
Sadly, there were also two related deaths. After being criticized for failing to report the disease among their birds, an elderly Japanese poultry farmer and his wife committed suicide.
It should be understood that, as Barry points out, the "natural home" of all forms of flu is in birds." Wild birds, particularly waterfowl and among them mallards, are natural carriers of milder avian influenza viruses. These infect the birds' stomachs and intestines. Their droppings contain large amounts of the virus which contaminates lakes and streams, thus spreading the disease.
The natural resistance of wild birds prevents them from becoming seriously ill. However, domesticated birds like chickens, ducks and turkeys and pet birds have no such resistance and can become sick from exposure to the milder forms. The virus can also mutate in these birds into HPAI and then whole flocks can die.
Pigs can also become infected with HPAI and become vectors. For this reason the human flu strains in 1976 and 2002 were called swine flu. Flu has also been recorded in seals, a whale and a mink.
What saves us, Barry says, is that "massive exposure to an avian virus can infect man directly, but an avian virus cannot go from person to person. It cannot, that is, unless it first adapts to humans." Fortunately, he adds, "The disease is considerably different in birds and humans."
It is the possibility that an HPAI will mutate still further to a strain that may be communicated among us that it becomes of human concern.
The particular strain of HPAI (H5N1) that is currently spreading through the Orient is unusual in that, according to veterinarian Dr. Carol Cardona of the University of California, "it can not only infect humans, but it can also make wild birds, especially ducks, sick." It will be interesting to see how this plays out in the weeks ahead.
Researchers agree, however, that culling wild birds is an inappropriate defense against this outbreak.-- Gerry Rising
For additional information about avian flu and flu in general, the following sites are informative: