Poliomyelitis strain spreads to China: Is U.S. at risk?

Is polio a thing of the past? In most of the world, poliomyelitis has been eradicated. But the crippling disease is still endemic to some nations - Pakistan, Afghanistan, Nigeria and India. This week, one nation will be checked off that list. On Friday, India will celebrate a full year since its last reported case of polio.The polio virus attacks the central nervous system, sometimes causing paralysis, muscular atrophy, deformation and, in some cases, death. It usually infects children in unsanitary conditions. In India, many vaccinated children fell ill with the virus because malnutrition and chronic diarrhea had weakened their bodies.Keep clicking to see photos of the disease being treated in India, as well as photos of others once affected around the world...
World Health Organization
Poliomyelitis remains threat in many countries. This undated photo shows polio patients are in Sierra Leone.
World Health Organization

(CBS/AP) Think poliomyelitis is a thing of the past? Polio is still a threat in several countries, including Afghanistan, India, Nigeria, and Pakistan - and the World Health Organization is warning that a "dangerous" strain of polio has spread from Pakistan to China.

PICTURES - Poliomyelitis: 15 photos spotlight crippling disease

A genetic link has been confirmed between wild poliovirus type 1 (WPV1) detected in China and a strain circulating in Pakistan, the organization says. In the past two months, there have been seven confirmed cases involving the WPV1 strain detected in China's Xinjiang province, which borders Pakistan, according to the organization.

WHO spokesman Oliver Rosenbauer says type 1 is more dangerous than type 3 because it is more likely to cause paralysis and spreads more easily. Type 2 polio has been eradicated.

The global health body says countries should strengthen their disease surveillance systems and travelers to Pakistan should be vaccinated against polio.

Polio is a crippling and potentially fatal infectious illness. It spreads through food and water and from one person to another via the fecal-oral route - meaning contact with the stool of an infected person. There is no cure, but there are effective vaccines.

There is no known risk of catching wild polio virus in the U.S., but the CDC says the disease remains a risk to travelers to certain countries. Anyone heading to one of these countries should first check with a doctor to review his/her polio vaccination status.

The World Health Organization has more on poliomyelitis.