What
is a pandemic?
A pandemic or global epidemic is an outbreak of an infectious
disease that affects people over an extensive geographical area like
a continent, hemisphere or the entire world.
How
do pandemics occur?
Pandemics can occur when three conditions have been met. They are
¨ the emergence of a disease new to the population,
¨ the disease agent (germ) infects humans, causing serious disease,
¨ the disease agent spreads easily and is sustainable among humans.
The
risk of a new influenza (flu) pandemic.
A new influenza virus has been circulating in the world particularly
in south east Asia for the last eight years. This virus named H5N1 strain
causes a disease called the Avian Influenza commonly known as the bird
flu. Bird flu is a severe illness of birds, particularly domestic poultry,
that often results in death within 48 hours. Though this infection is
normally confined to birds and pigs it can and does at times spread
to humans who are in close contact with these birds. Since 2003 more
than 100 cases of bird flu have been confirmed in humans from four Asian
countries namely Cambodia, Indonesia, Thailand, and Viet Nam and half
of these have died. The disease till now has not spread from human to
human. But scientists fear that the virus may undergo changes very soon
that would enable it to spread from human-to-human. Once this occurs
all the conditions necessary for a pandemic to occur (as mentioned above)
would be fulfilled heralding the onset of another influenza pandemic.
Is Bird Flu spreading?
Bird flu that began in South-east Asia in the year 1997 has
begun to spread to other countries and has now been reported in countries
like Russia, Kazakhistan, Mongolia and even Turkey and Romania. Though
human cases have not been reported outside South East Asia it is only
a matter of time before humans get infected.
How
serious is the risk for a new influenza pandemic?
The risk for the occurrence of a new pandemic is quite high. Since the
H5N1 strain is well entrenched in several countries the chances of humans
getting the infection from the birds are high. Each additional human
case gives the virus an opportunity to improve its transmissibility
in humans, and thus develop into a pandemic strain.
How
can the bird flu virus acquire the qualities to become a pandemic virus?
As mentioned above the only quality lacking
for the virus to cause a pandemic is its inability to easily spread
from human-to-human. But each time it infects a human it can come into
contact with a human strain of the flu virus that the person may already
be carrying. This permits the exchange of genetic material between the
two strains resulting in the avian strain acquiring the ability to spread
from human-to-human. When this happens the virus is ready to cause a
pandemic.
What
would be the consequences of the pandemic?
Since most of the people have no immunity to this new virus a large
number of people are likely to fall ill over a short period of time.
The pandemic of 1918 (called the Spanish flu) killed about 50 million
people. Today, with the increase in the world population and the ease
of international travel the number of people that would be affected
would be far higher. But the risk of fatality depends upon a number
of factors that cannot be determined till the pandemic has actually
begun and thus the fatality rate cannot be accurately predicted at this
time. Despite these limitations the World Health Organization has predicted
that there maybe as many as 7.4 million deaths during the pandemic.
Can
the pandemic be prevented?
The best way to prevent the pandemic would
be to eliminate the virus from the birds. Efforts towards this have
been underway. Methods of control of avian flu include vaccination,
destroying the birds that have been infected and preventing importing
of birds from endemic areas. But so far these has not met with much
success. China has recently vaccinated millions of birds with a novel
oral vaccine. But how far this would succeed needs to be seen.
Will antiviral drugs be useful in controlling the
pandemic when it occurs?
Antiviral drugs will definitely be useful in controlling
the spread of the disease to an extent. But the problem with this is
that there may not be enough antiviral drugs to go around when the pandemic
strikes, particularly if it spreads explosively.
The
role of vaccines.
Vaccines to be effective against the pandemic must closely resemble
the pandemic virus. Therefore it follows that vaccines cannot be produced
till the pandemic breaks out. This means that effective vaccine will
not be available till the pandemic becomes well established.
The
role of WHO in controlling the pandemic.
WHO has prepared guidelines for controlling the pandemic when it occurs.
Member countries including ours should follow these guidelines and be
prepared to control it. Much depends upon the willingness and the preparedness
of the various governments and other agencies to tackle this public
health problem which will have very serious repercussions on the health
and economy of the world at large.
