Meanwhile, a separate polio outbreak is ravaging Nigeria, where the outlook is similarly grim.
As of September 1, Nigeria reported 785 cases of polio, compared to 434 at the same time last year. The African nation currently accounts for about 70 percent of the world's polio cases.
According to Brandao Co, head of the UN's Expanded Program on Immunization in Nigeria, most of the country's polio cases are in northern Nigeria, where the situation is reaching epidemic proportions (see Nigeria map).
Moreover, increased global travel is providing the virus with new pathways of infection, experts warn.
Cases of polio associated with the current outbreaks have already been reported in Bangladesh, Nepal, Yemen, Angola, Namibia, and Indonesia, prompting large-scale immunization drives in those nations.
"As long as a single child remains infected with wild poliovirus in one country, children in all countries are at risk," Co, in Nigeria, said.
Polio, or poliomyelitis, is a crippling disease that mainly targets children under five years of age. It is caused by a virus transmitted through drinking water tainted with fecal matter or through saliva.
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The virus spreads quickly through a child's nervous system, wreaking havoc on the nerve cells that activate muscles.
One in 200 infections leads to irreversible paralysis, usually in the legs, within a few hours. In about 5 to 10 percent of these cases, an infected child dies when the paralysis reaches the muscles used for breathing.
Transmission of the wild poliovirus was interrupted in the United States in the late 1970s, and according to the U.S. Centers for Disease Control and Prevention (CDC), it was eliminated from the Western Hemisphere in 1991.
A global UN vaccination campaign launched in 1988 to eradicate the disease has been 99 percent successful, reducing the number of worldwide polio cases from more than 350,000 in 1988 to less than 700 in 2003.
Along with India and Nigeria, Pakistan and Afghanistan remain the only four nations where polio is currently endemic, or native to the region.
But reports of new cases of polio have begun appearing in several previously polio-free countries in recent months, causing health officials to worry that the new infections could seriously compromise the global effort against polio.
"It is a tragic setback," said Jeffrey Bates, a spokesman for the United Nations Children's Fund (UNICEF) in New York.
"We have to divert resources from endemic areas to reinfected areas. It dilutes our response and will lead to substantial input of resources by recipient countries to stop transmission."
Genetic tracking of the virus suggests that the outbreaks are spreading from India and Nigeria by infected travelers.
"The outbreak in Indonesia earlier this year can be traced to the Nigerian strain, which previously caused outbreaks in Sudan and Saudi Arabia," said Hamid Jafari, regional advisor to WHO in New Delhi, India.
"The Uttar Pradesh virus has since found its way to Bangladesh and Nepal. Last year there was an outbreak in Angola, which then spread to Namibia. That virus was also from Uttar Pradesh."
Experts in India and Nigeria blame the outbreaks there on factors such as high population density, poor sanitation, environmental degradation, and other diseases.
"The presence of other intestinal viruses affects the efficacy of the polio vaccine," UNICEF's Bates explained.
"When these viruses get into the food tract and interact with the vaccine, the immune system is compromised."
Less developed countries have to administer the vaccine several times for it to be effective, he says, and many families fail to present their children for repeated vaccinations.
Experts in both countries now think that this year's outbreaks could largely be due to immunization campaigns that missed a significant percentage of children in 2005.
But rumors about the side effects of the polio vaccine may also be amplifying the outbreaks.
Nearly 70 percent of reported polio cases in India are among Muslim children, according to WHO.
"We tend to miss more children in Muslim areas," said Wenger, of India's National Polio Surveillance Project.
"There seems to be some degree of reluctance to accept the vaccine, and this is reflected in numerous newspaper articles and the occasional fatwa [Islamic religious ruling]."
WHO's Jafari in New Delhi believes the local media there are compounding the problem.
"There is a lot of misinformation in newspapers and the media about the safety of the vaccine," he said.
Some communities believe the polio vaccine makes children impotent and sterile. Press reports in Urduthe language of many South Asian Muslimshave helped propagate the myths. In some areas of Moradabad, vaccination teams have even been attacked for trying to administer immunizations.
In Nigeria Muslim leaders suspended vaccination campaigns in 2003 because of rumors that the vaccine was laced with HIV and infertility drugs.
Co, of the Nigerian vaccination program, said that the misinformation has nearly undone the progress made in his region.
"The safety controversy about the oral polio vaccine raised by some Islamic scholars in mid-2003 has reversed all the gains in polio eradication up to 2002 in Nigeria," he said.
Both countries, however, are initiating new steps to tackle the growing infections.
In Nigeria, officials have launched a radical new campaign called Immunization Plus Days, in which communities are offered additional benefits to polio vaccination, including immunization against measles, diptheria, pertussis, and tetanus, as well as doses of Vitamin A and deworming tablets.
In India similar efforts are being strengthened to stop the outbreak in western Uttar Pradesh.
Health officials are teaming up with local leaders to ensure greater coverage for immunization, administering a new oral polio vaccine that offers greater protection with fewer doses than the traditional vaccine.
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