Posted at 12:52 a.m., Tuesday, April 2, 2002

U.S. says world close to eradicating polio scourage

By Paul Simano, Rueters science writer 

ATLANTA, March 28 - U.S. health experts said on Thursday that the number of confirmed polio (news - web sites) cases in the world dropped 34 percent last year, bolstering hopes that the once-common crippling disease might be eliminated this decade.

The Centers for Disease Control and Prevention (news - web sites) said 473 cases of polio were confirmed by laboratories around the world in 2001, down from 719 the previous year and a far cry from the estimated 350,000 reported before the beginning of a global eradication campaign in 1988.

Polio, which once afflicted millions of children, attacks the central nervous system, often causing paralysis, muscular atrophy and deformity. Five to 10 percent of those infected die when their breathing muscles become paralyzed.

The scourge, usually contracted through exposure to contaminated water, largely disappeared from the Western world as a result of vaccination programs begun in the 1950s, but it still exists in a handful of Asian and African nations.

India, Pakistan and Nigeria accounted for 92 percent of all cases last year.

While acknowledging that the combination of large, dense populations, poor sanitation and traditionally low vaccination rates were serious obstacles, the CDC said inroads were being made in these remaining polio-afflicted nations.

"These three countries benefit from as many as four to six mass vaccination campaigns during the year and we are hopeful that this should be able to finish the job over the next 12 to 24 months," said Dr. Patrick Zuber, an epidemiologist who works in the CDC's National Immunization Program.

The World Health Organization (news - web sites) wants to eradicate polio globally by 2005, but the effort has been hampered by a lack of funds, civil wars and political intransigence in affected countries.

Federal health experts said the best hope for conquering polio was to adopt a strategy that included mass vaccinations to immunize millions against the wild form of the virus as well as efforts to prevent the spread of vaccine-derived polio.

Wild polio, which exists in only 10 countries, can be prevented with a three-dose oral vaccine that contains an altered live form of the polio virus. In rare cases, the virus can reactivate inside a vaccinated person and escape into the environment through feces.

Once in contact with the water supply, the virus then reverts to its wild strain and is free to spread to others who have not been immunized, as occurred during an outbreak in 2000 and 2001 in Haiti and the Dominican Republic.

Twenty-one people contracted polio during the outbreak, including two children who died. Zuber said it was important for countries to continue mass vaccination programs for a certain period after the elimination of wild polio in order to prevent such outbreaks in the future.