Polio infections are increasing and spreading to new countries, says a World Health Organization report.

Since April, outbreaks have been found in 10 countries beyond the 4 in which polio is considered endemic — Afghanistan, India, Nigeria and Pakistan. And in those four countries, the number of cases has more than doubled in just one year.

In Africa, cases have been found as far south as Angola and as far west as Ethiopia. Each detected case implies another 200 cases with few or no symptoms, experts say.

Pakistan, which has seen a rapid rise in cases, now has 86,000 vaccination teams going house to house and dosing children at train stations and border crossings. But tribal areas on the Afghan border and neighboring parts of Afghanistan are barely covered because travel is unsafe for vaccinators.

The Indian Academy of Pediatrics has endorsed adding injectable vaccine as a backup for those who can afford it, because it can protect children whose oral doses are eliminated by diarrhea, a common ailment in these parts.

Polio is a contagious, historically devastating disease that was virtually eliminated from the Western hemisphere in the second half of the 20th century when a vaccine became widely available.

Polio is a viral illness that, in about 95% of cases, actually produces no symptoms at all (called asymptomatic polio). In the 4% to 8% of cases in which there are symptoms (called symptomatic polio), the illness appears in three forms:

• a mild form called abortive polio (most people with this form of polio may not even suspect they have it because their sickness is limited to mild flu-like symptoms such as mild upper respiratory infection, diarrhea,, fever, sore throat, and a general feeling of being ill)
• a more serious form associated with aseptic meningitis called nonparalytic polio (1% to 5% show neurological symptoms such as sensitivity to light and neck stiffness)
• a severe, debilitating form called paralytic polio (this occurs in 0.1% to 2% of cases)

People who have abortive polio or nonparalytic polio usually make a full recovery, but those with paralytic polio, as its name implies, causes muscle paralysis - and can even result in death. In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream, attacking the nerves. The virus may affect the nerves governing the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs.

Polio is transmitted primarily through the ingestion of material contaminated with the virus found in stool (poop). Not washing hands after using the bathroom and drinking contaminated water are common culprits in the transmission of the disease.

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