NEW DELHI, Feb. 19 — The first reports of bird flu that cropped up in recent days in widely separated countries — India, Egypt and France — highlighted the disease's accelerating spread to new territories.

International health experts have been predicting widespread dissemination of the disease for about half a year, since they concluded that it could be spread by migrating birds. But the recent acceleration has perplexed many experts, who had watched the A(H5N1) virus stick to its native ground in Asia for nearly five years.

The most alarming of the current outbreaks, if only for sheer size, were the two widely separated episodes of avian flu in India, one of which has killed 50,000 birds in poultry flocks in the last few days. The Indian government, which has long been on alert for the virus because that country is on many migration paths in Asia, began killing half a million birds in the hopes of quashing the outbreaks, officials announced Sunday.

But the most perplexing report involved the single case in France — a wild duck found dead in the suburbs of Lyon — because migratory birds from Asia that carry the virus do not normally travel there at this time of year.

"After several years in one place, why is it now moving so rapidly?" asked Dr. Samuel Jutzi, director of the Animal Production and Health Division at the United Nations Food and Agriculture Organization in Rome. "There is a lot about this that we just don't know."

The dead duck in France, he said, was "very odd, very difficult to explain." But he added, "What is known is that the width of flyways are very broad, and there may have been a swarm that went farther westward than normal."

In Western Europe, the disease has been confined to wild migratory birds, and authorities across the Continent were taking severe measures to protect domestic poultry. Many countries are now requiring that all poultry be kept indoors to prevent mixing with potentially infected wild birds.

In recent days, a wild duck in central Italy was also found dead from the virus, the first time it had been found so far north in that country.

On the German island of Rügen in the Baltic Sea, 18 wild birds were confirmed to have the disease, bringing the total of infected birds there to 59 in the past week, mostly swans and hawks. The German chancellor, Angela Merkel, visited the island on Sunday, a sign of how seriously European governments are taking the disease.

Germany is preparing to kill at least some of the 400,000 domestic birds on the island to make sure the virus does not spread into poultry flocks, local authorities said. When bird flu is detected in an area, the most effective way to control an outbreak is to kill all the birds in a surrounding area to isolate the highly infectious virus, and to ban movement of poultry in and out of the area.

But in India the disease is already in farm birds, raising more complicated issues, and the possibility that there will be human infections. Although the dreaded virus does not now readily infect humans or spread among them, more than 160 people have caught the disease worldwide, all of them people who had close contact with sick birds.

Experts are worried that A(H5N1) could acquire the ability to spread from human to human through natural processes, setting off a worldwide influenza pandemic.

Government officials in a rural district of western India on Sunday began to slaughter and inoculate roughly a million chickens, and dozens of people from the same area were dispatched to be tested, a day after test results confirmed the first outbreak of avian flu in this country.

Officials in New Delhi took pains to dismiss earlier press reports of a poultry farmer's death from suspected bird flu. The central government ordered state governments to step up surveillance efforts, urged the public to "maintain proper hygiene and sanitation," and announced that it was taking steps to increase the availability of bird flu treatment in India.

If it is not swiftly contained, bird flu could be disastrous in this country, where the population density and a feeble public health system, especially in the countryside, make it particularly vulnerable to a pandemic of this sort. India is the world's sixth-largest poultry producer, according to the United States Department of Agriculture.

The poultry deaths took place in a district called Nandurbar, near the northern border of Maharashtra State. State health officials said by telephone that 68 people were being tested for the virus. Workers in the 16 poultry farms in the area, which until two days ago had exported poultry to neighboring states, had tested negative for the virus.

The home minister of India, Shivraj Patil, announced Sunday that chickens within a two-mile radius of the outbreak would be killed while others within six miles would be inoculated. A statement issued late Saturday by the central government information bureau said that the situation was "under control."

News reports on Saturday suggested that a 27-year-old poultry farmer, also in the Nandurbar area, had died of bird flu. On Sunday, the Indian government announced that "preliminary" test results had been negative.

About 50,000 poultry are reported to have died from the infection in recent days in the western state of Maharashtra. Officials were also testing for the A(H5N1) strain in India's most populous state, Uttar Pradesh, after 1,400 birds died at a farm there.

United Nations health officials have long urged the governments of India and Egypt to be on high alert for bird flu.

But Dr. Jutzi, the United Nations health official, and other international experts added that the extent of the problem was still unclear in those two countries.

"How extensive the problem is in India is still not known," said Juan Lubroth, a senior veterinary official at the Food and Agricultural Organization, who said the United Nations first received an alert about the outbreak on Friday, and reports from India's states were still coming in.