Polio rebounds in Nigeria24th August 2009
Some Nigerians are suffering from a variety of polio previously thought to have been eradicated.
The variety, known as type 2 poliovirus, was eradicated about a decade ago, but has now caused over 100 cases of paralysis in a Nigerian outbreak.
Poliovirus, which is also known as poliomyelitis due to the effect the disease can have upon the spinal cord, has been known to cause paralysis since the dawn of history.
Some Egyptian paintings depict young children or otherwise healthy individuals walking with canes.
Poorer sanitation standards prior to the 20th century caused constant exposure to the polio virus in many populations, and many people were naturally immune to it.
But small-scale epidemics began to happen in Europe and the United States around the turn of the 20th century, and with the advent of cleaner water and efficient sanitation systems, the disease gradually became pandemic in many parts of the Northern Hemisphere.
The recent Nigerian outbreak is due to the fact that the oral polio vaccine (OPV), developed in 1962, makes use of type 2 poliovirus.
The OPV, developed by Albert Sabin, uses live “attenuated” virus specimens.
The specimens are repeatedly passed through non-human cells at very low temperatures, which renders it mostly harmless against nerve tissue.
But now, the same vaccine has mutated among the Nigerian population and regained its paralytic power over the human body.
Experts had feared this might happen, since OPV is known to paralyse in some 1 in 100 cases.
However, OPV is cheaper and easier to administer, and has been used in Nigeria since 2005.
Experts are uncertain whether or not the outbreak is due to an increased vulnerability among children to type 2 poliovirus, but vaccination campaigns in Nigeria usually focus on polio types 1 and 3.
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