The swine flu virus did not result from a laboratory accident, the World Health Organization said Thursday, working to debunk rumors started by an Australian virologist and circulated by news outlets all over the world.“We took this very seriously,” Dr. Keiji Fukuda, the agency’s deputy director general, said of the virologist’s assertion. “But the evidence suggests that this is a naturally occurring virus, not a laboratory-derived virus.”In a telephone news conference, Dr. Fukuda also expressed support for drug companies’ making a generic version of the antiviral drug Tamiflu. Many poor countries have no stockpiles of the drug.Almost 6,500 confirmed cases of the new H1N1 flu have been reported from 33 countries, and 65 people have died, the W.H.O. said. About 4,300 confirmed and probable cases, with 3 deaths, were reported in the United States.A woman in Arizona who was suffering from lung disease died last week from complications of swine flu, the Maricopa County Department of Public Health said late Thursday, Reuters reported.The virus rumor was started by Adrian J. Gibbs, a retired plant virologist from the Australian National University, who previously published work in the journal Science questioning the idea, now accepted, that the 1918 pandemic started as a bird flu.Dr. Gibbs, who had studied the gene sequences of the swine flu virus posted on public data banks, argued that it must have been grown in eggs, the medium used in vaccine laboratories. He reached that conclusion, he said, because the new virus was not closely related to known ones and because it had more of the amino acid lysine and more mutations than typical strains of swine flu.His theory was reported by Bloomberg News on Tuesday. Even though scientists at the Centers for Disease Control and Prevention were skeptical and some prominent virologists openly derisive, news outlets have repeated and magnified the theory, adding speculation about bioterrorism that even Dr. Gibbs repudiated. He was also interviewed Thursday on the ABC News program “Good Morning America.”Dr. Fukuda said a W.H.O. panel of experts had concluded that “the hypothesis does not really stand up to scrutiny.” The lysine residues and mutation rates were typical, he said, and many swine flus seem unrelated because not enough pigs are tested each year.But he added that he doubted that the rumor would prove damaging, and he said he would not want genetic sequences kept off public databases.“This is healthy,” he said. “This is much better than dealing with rumors where you don’t know where the mistake comes from and can’t correct it.”Persistent false rumors, like those that AIDS is not caused by a virus or that polio vaccine sterilizes Muslim girls, have devastated efforts to control other diseases.Scientists have yet to pinpoint the origin of the swine flu virus, the earliest cases of which were found in Veracruz, Mexico. It contains genes from flu viruses that normally circulate in pigs in Europe and Asia, as well as avian and human genes.Late Thursday, Smithfield Foods reported that the Mexican health authorities had not found the new virus in herds at its huge hog-fattening operations in Veracruz, which some have blamed for the outbreak. But it was not clear what test was used; only blood tests for antibodies would show whether pigs had the virus in February, when the human outbreak is thought to have begun.As for the use of oseltamivir, the generic form of Tamiflu, the W.H.O. has certified only one drug — Antiflu, made by the Indian company Cipla in both pill and liquid forms — as equivalent to brand-name Tamiflu.Dr. Yusuf K. Hamied, Cipla’s chairman, said he would sell large amounts to Mexico and was in discussion with countries in Africa, Latin America and the Middle East.The move could prompt patent lawsuits by Gilead Sciences and Roche, which developed and sell Tamiflu, so Cipla will sell only to countries indemnifying them against such suits, the company said.Roche has offered 6.5 million doses of Tamiflu to the World Health Organization and 1 million doses to Mexico.Dr. Hamied, reluctant to buy supplies for orders that might not materialize, said that poor countries should stockpile shikimic acid, the oseltamivir precursor, then pay Cipla or other generic companies to make the drug as needed.The swine flu may cause the W.H.O. to cut short its nine-day annual conference of world health ministers so they can get home to fight the disease, Reuters reported.Source: New York Times