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Monday, June 10, 2013
H7N9 Bird Flu - Who Is at Greatest Risk of Dying?
Avian influenza or "bird flu" has now caused more than 60 deaths
worldwide, with the most recent epidemic in Indonesia, where four people
have died. On a global basis, 60 deaths are not very many. So why are
health experts becoming alarmed about the H5N1 ("bird flu") virus?
People are concerned because the virus has demonstrated the ability to
kill a high percentage of the humans it infects. In addition, it has
spread from birds to many other species, which is very uncharacteristic
of viruses. The spread of infection in birds increases the opportunities
for direct infection of humans. If more humans become infected over
time, the likelihood also increases that humans, if concurrently
infected with human and avian-influenza strains, could serve as the
"mixing vessel" for the emergence of a novel subtype-with sufficient
human genes to be easily transmitted from person to person.
the virus acquires the capability to "go human," an influenza pandemic
(that is, a worldwide epidemic) would likely ensue in a matter of weeks.
To date, the vast majority of infections of bird flu in humans have
been acquired by close contact with domestic poultry. However, there is
one documented case of human-to-human transmission in Thailand. It
remains a curious fact that most people who have worked with poultry
infected with the bird-flu virus, culling infected birds for example,
have not become infected-a fact that no one seems able to adequately
The antigenic changes (that is, changes in the exterior
proteins-Hemagglutinin and Neuraminidase) in bird and human influenza
viruses go on year after year. Annual influenza outbreaks typically do
not cause severe illness and death, because people have built up natural
immunity to the viruses over a period of years. Rapid spread of H5N1
viruses between humans, on the other hand, will led to explosive global
expansion in which everyone is at risk for infection, illness, and death
because of a complete lack of natural immunity to the virus.
avian influenza or "bird flu" is much more deadly than the regular
annual flu in humans, coupled with the high infectiousness of influenza
viruses in general, a bird-flu pandemic is potentially very deadly,
causing many tens-or even hundreds-of millions of deaths across the
globe. In September 2005, Dr. David Nabarro of the World Health
Organization (WHO) stated, "A new pandemic would claim between 5 million
and 150 million people."
Once a flu pandemic starts, everyone
will be at risk of getting pandemic flu, because no one has natural
immunity to the virus. However, certain groups may be at greater risk of
dying than others. There are strong indications that the coming
bird-flu pandemic may be similar to the influenza pandemic of 1918 and,
if so, healthy adults would be most at risk of dying, along with
pregnant women and the elderly.
Why are healthy adults at
greatest risk? It appears that the H5N1 bird-flu virus causes a massive
immunological response against the virus in those with the strongest
immune systems. Unfortunately, this causes the release of human enzymes
called "cytokines," which destroy lung cells along with viral
particles. This, in turn, causes a deadly outpouring of fluids into the
lung, which interferes with the exchange of oxygen and carbon dioxide.
This reaction is frequently fatal. There are few effective
treatments-one of the only treatments available is to place the patient
on a ventilator, a mechanical respirator. Even with this treatment,
patients often die from complications.
Bradford Frank, M.D., M.P.H., M.B.A. The Frank Group P.O. Box 138 Lakewood, NY 14750 www.AvoidBirdFlu.com