Highly Pathogenic Avian
Influenza
(This column was first published in
the March 21, 2004 issue of The Buffalo News.)
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: