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.
Once 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 explain.
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.
Because 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