Jaqur Nisha kisses her son Mohammad Sajid, 2, afflicted by Japanese encephalitis, in Gorakhpur, India

The World Health Organization says India is starting to halt a recent outbreak of Japanese encephalitis that has killed more than 800 people. The disease, which is caused by mosquitoes and is most prevalent during the annual monsoon, may be better contained next year, with officials hoping to launch a new vaccination campaign.

Several-thousand cases of Japanese encephalitis have been reported in India since the end of July, almost all of them in the northern province of Uttar Pradesh. More than 800 patients have died, most of them children.

But the World Health Organization says it appears that the Indian health authorities now have a handle on the outbreak. Brent Burkholder is an immunization expert in the Southeast Asia regional office of the WHO, whose territory includes India.

"It looks like the cases have started to come down, and we would expect that the number that we will be seeing now will be certainly decreasing over the next month or so," said Brent Burkholder.

There are minor outbreaks of Japanese encephalitis in India and Nepal every year, coming with the annual monsoon rains. It is not clear why this year has proven worse, except that diseases are sometimes cyclical in nature.

Mr. Burkholder says India's last large outbreak of Japanese encephalitis took place ago four to five years ago, which is consistent with the disease's approximate cycle.

He also says there are reasons for hope that outbreaks in the future will not be as serious. Mr. Burkholder says both India and Nepal have told the WHO they want to launch immunization campaigns against Japanese encephalitis, perhaps with a new vaccine currently being developed in China.

"Probably this will require a campaign-type of approach that would look at trying to target the high-risk areas and the high-risk age groups - probably children up to a certain age, up to age 10, in some areas maybe a little bit higher," he added.

Mosquitoes transmit the Japanese encephalitis virus from pigs or birds to human beings, who can suffer brain damage from it. In about a quarter of the cases, the disease is fatal.

The outbreak is occurring just as India is working hard to attract international patients, with low prices for state-of-the-art health care. In some cases, treatments can cost thousands of dollars less than they would in developed countries.

In India's defense, Mr. Burkholder says even the most developed nations can experience serious disease, noting the outbreaks of the West Nile virus in the United States in recent years.