Outbreak An Approaching Nightmare
SARS first surfaced, health experts were fearfully watching
whether another wave of flu nightmare was going to happen,
which is due over long time. Scientists finally found another
deadly virus, which visited more than 20 countries within
few months, infected over 8000 people and finally ended
with more than 800 lives.
recent Bird flu outbreak is a reminder of the nightmare,
during World War I. Although Bird flu usually does not infect
humans but may pave the way for killer flu pandemic. The
Spanish Flu (a misnomer, since it had nothing to do with
Spain) would perhaps be better called the "Forgotten
Plague". Despite devastating the planet in 1918, causing
over 30 million deaths, this epidemic has been forgotten
except by a few researchers.
in October 1917, a benign human influenza virus jumped into
a pig in USA and underwent a random mutation and turned
out to be a universal killing machine within a few months
.A chain reaction began, soon engulfing the world. Some
people fell ill and died within a matter of hours. New York
commuters boarded their trains healthy and were dead upon
arrival in the city. Unusually, the virus targeted healthy
young people, killing them preferentially over older individuals.
Panic broke out in cities around the globe as hospitals
and morgues filled with the dead and dying. In the United
States, troop camps were disbanded and emergency health
measures instituted. In other places the result was far
worse. Half the population of some Pacific islands was wiped
out in this epidemic. Untold millions died in Asia. The
Spanish flu took the country by storm during another time
of crisis- World War I. This factor aided the spread of
the disease considerably. As soldiers travelled from port
to port, they brought with them flu germs as well as their
weapons. The virus stalked everyone, everywhere. There was
no hiding place and there was no cure. One could only hope
not to become infected. Astonishingly, the lethal killer
disappeared without any trace after 18 months of rampage.
are chasing over time, following the footprint of the deadly
virus. After 45 years of outbreak, they traced out the remnant
of genetic material from a 1918 flu-infected dead body,
exhumed from Alaska and finally decoded the genetic material
of this deadly flu. From the evolutionary path it can be
categorically seen that that virus comes from pig. Experts
believe that the descendent of the Spanish flu still is
alive in wild birds especially, duck and fowl, and will
come back again with lethal power.
has experienced a couple of flu outbreaks after the Spanish
flu. Outbreaks in 1957-58 and in 1968-69 caused a million
deaths each time. The length of time between the last major
outbreak and now is what's making observers nervous.
are three types of influenza virus-A, B, C, all of which
can infect humans.
Influenza type A viruses are found in many different animals,
including ducks, chickens, pigs, whales, seals and horses.
There are Fifteen subtypes of influenzas.
A are known to infect birds (chickens and ducks included),
named as Avian or Bird flu virus, which was first identified
in Italy more than 100 years ago, occurs worldwide. All
birds are thought to be susceptible to infection with Avian
influenza virus (some migratory birds, especially wild ducks
are resistant to infection and may act as carriers to ferry
the germs place to place). To date, all outbreaks of the
highly pathogenic form have been caused by influenza A viruses
of subtypes H5 and H7 variant of bird flu virus.
are the simplest form of life. They are little more than
a set of instructions, coded in DNA or RNA (genetic material),
for reproducing themselves. Part of their cunning is that
viruses don't carry their own reproductive machinery. When
a virus floats in the air, or sits on a door handle, it
is inert. When it gains access to a suitable living cell,
it springs into action, hijacking the cell's machinery to
replicate itself before moving on. Viruses get inside the
cell using the proteins on its outer coating. They are like
keys that match up with receptors on the outside of the
cell to allow the virus inside. Once in, it copies itself
again and again. These copies have the same urge to replicate,
and so they "bud" out of the cell membrane into
the host's body where they find another suitable cell and
start the process again.
flu virus is able to mutate faster than almost any other
virus. Every year there is a slight drift or mutation in
the virus' genetic instructions due to lack of mechanisms
of proofreading or repair of errors that occur during replication,
allowing it to constantly evade the immune systems of its
hosts. That's why flu shots must be given every year in
order to be effective. While drift is responsible for the
annual outbreaks of flu, things can get really nasty when
the virus undergoes a sudden genetic "shift" ?
usually through recombination with another strain, perhaps
from a pig or bird. Most striking feature of flu virus is
that, its genetic material is segmented. Whenever two different
variants of flu virus infect a single animal, the consequence
would be a brand new killer virus due to drastic genetic
reassortment. Only pigs can be infected with both human
and bird flu viruses in addition to swine influenza viruses.
Because pigs are susceptible to avian, human and swine influenza
viruses, they potentially may be infected with influenza
viruses from different species (e.g., ducks and humans)
at the same time. If this happens, it is possible for the
genes of these viruses to mix and create a new deadly virus.
is H5N1 of particular concern: Of the 15 Avian influenza
virus subtypes, H5N1 is of particular concern for several
reasons. H5N1 mutates rapidly and has a documented propensity
to acquire genes from viruses infecting other animal species.
Birds that survive infection excrete virus for at least
10 days, orally and in faeces, thus facilitating further
spread at live poultry markets and by migratory birds. The
epidemic of highly pathogenic avian influenza caused by
H5N1, which began in mid-December 2003 in the Republic of
Korea and is now being seen in other Asian countries, is
therefore of particular public health concern. H5N1 variants
demonstrated a capacity to directly infect humans in 1997,
and have done so again in Viet Nam in January 2004. The
spread of infection in birds increases the opportunities
for direct infection of humans. So far, the good news is
that viruses leave not yet learnt how to transmit human
to human. 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. Such an event would mark the start of an influenza
would happen if another virulent mutation struck in a world
much more populous and interconnected than in 1918? It is
not clear that modern medicine and health systems are any
better prepared than in 1918. The world is entering a profoundly
dangerous era of emerging diseases. Humanity sits on a biological
time bomb. A new Hiroshima is approaching, and mankind is
unprepared for this approaching apocalypse that may rewrite
the future of our planet.
Mohammad Sorowar Hossain, the writer is Research Fellow
Virology Lab, National University of Singapore Sorowar@tll.org.sg