Criminals are using the Internet to sell increasing quantities of counterfeit medicines, including fake versions of bird flu drug Tamiflu, a senior U.N. health expert said on Tuesday.

Vitamin and health supplements, so-called “lifestyle medications” like erectile dysfunction drugs, and steroids bought over the Internet are especially likely to be false.

Antibiotics, antimalarials and painkillers are also susceptible to fraud because of the huge demand, while Tamiflu, made by Swiss firm Roche, has also entered the market amid rising avian flu fears.

“Yes, there have been cases reported in counterfeit Tamiflu,” said Howard Zucker, the World Health Organisation’s assistant director general for health technology and pharmaceuticals.

But he declined to give details on the quantity or where the fake drugs had been found. The WHO has estimated as many as 10 percent of drugs on the world market are mislabeled or fake, with the phony medicines sometimes causing illness and even death in consumers.

Speaking to reporters after a high-level meeting in Rome, where pharmaceutical industry and health experts agreed to set up a task force to fight the counterfeit drug trade, Zucker said better oversight of online drug sales was essential.

At the meeting, the U.N. health body said it will help set up an international expert group to raise awareness about fake drugs and to improve cooperation among governments, industry groups and international agencies on the issue.

“Counterfeiting medicines should be distinguished from other types of counterfeiting, which do not affect human health and should be combated and punished accordingly,” the conference participants said in a statement at the end of their meeting.

Harvey Bale, director general of the International Federation of Pharmaceutical Manufacturers Associations, said fake medicines remain more prevalent in developing countries than in places like Western Europe.

Still, Bale stressed patients in the wealthier countries are increasingly vulnerable to counterfeit drugs distributed online. He said the new task force will look into that growing sector.

“The Internet needs to be addressed, clearly,” he said.