7.Catchy Coughs
They cause outbreaks, epidemics, even pandemics that spread from
continent to continent.
Modern medicine and hygiene have given us some
control over devastating infectious diseases, even eradicating smallpox,
but, for the most part they remain with us, often preying upon the
poorest and most vulnerable.
6.Smallpox
A photo taken in 1975 shows the village cemetery in the Bangladesh
countryside where smallpox victims were buried. The disease was believed
to have killed 46 percent of its victims at a hospital in the Dacca,
Bangladesh and to have ravaged the country for centuries. A disease
marked by lesions on the skin, smallpox is
believed to have emerged about 3,000 years ago in India or Egypt before
sweeping across continents. The variola virus, which causes smallpox,
killed as many as third of those it infected and left others scarred and
blinded, according to the World Health Organization. In 1980, the WHO
declared the disease officially eradicated, after a decade-long
vaccination campaign. The last known remaining samples of the virus are being held in facilities in the U.S. and Russia.
5.Plague
Unlike smallpox, this ancient killer is
still with us. Plague, which is caused by a bacterium carried by fleas —
like the one shown above — has been blamed for decimating societies
including 14th century Europe during the Black Death, when it wiped out
roughly a third of the population. The disease comes in three forms, but
the best known isbubonic plague,
which is marked by buboes, or painfully swollen lymph nodes. Plague is
now found in animals throughout the world, particularly in the western
U.S. and Africa. In 2009, the World Health Organization reported 958
cases worldwide.
4.Malaria
Although it is preventable and curable,
malaria has a devastating effect in Africa, where the disease accounts
for 20 percent of all childhood deaths, according to the World Health
Organization. It is present on other continents as well.
A parasite
carried by blood-sucking mosquitoes causes the disease, which is first
characterized by fever, chills and flu-like symptoms before progressing
on to more serious complications. By 1951, the disease was eliminated
from the U.S. with the help of the pesticide DDT.
A subsequent WHO
campaign to eradicate malaria was successful only in some places, and
the goal was downgraded to reducing transmission of disease, according
to the U.S. Centers for Disease Control and Prevention.
3.Influenza
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| This
3-D model illustrates a generic flu virus (there are different types). A
seasonal, respiratory infection, flu is responsible for about three to
five million cases of severe illness, and about 250,000 to 500,000
deaths, according to the World Health Organization. Periodically,
however, the viral infection becomes much more devastating: A pandemic
in 1918 killed about 50 million people worldwide. As we learned from
"swine flu" and "bird flu" scares in recent years, some influenza viruses can jump between species.
2.Tuberculosis
Potentially fatal "TB" is caused by the bacterium Mycobacterium
tuberculosis, which usually attacks the lungs causing the signature
bloody coughs. The x-ray above shows the chest of a patient suffering
from far-advanced tuberculosis. The bacterium does not make everyone it
infects sick, and up to one third of the world's population currently
carries the bacterium. And among people infected with TB, but not HIV, 5
to 10 percent become sick or infectious at some time during their
lifetimes. A full-blown TB infection is more common among those also
infected with HIV. The TB bacterium has formed a deadly alliance with
the immune-system-destroying HIV, with each disease worsening the other,
according to the World Health Organization.
1 HIV/AIDS
In 2009, about 33 million people were living with a Human
Immunodeficiency Virus infection and about 1.8 million died from it,
according to the World Health Organization. While many of the worst
offenders have a longstanding relationship with humans, HIV is a recent
arrival. HIV's decimating effect on certain immune system cells was
first documented in 1981. By destroying part of the immune system, HIV
leaves its victims vulnerable to all sorts of opportunistic diseases. It
is believed to have emerged from Simian Immunodeficiency Virus (SIV)
which infects apes and monkeys.
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