FORT LAUDERDALE, Fla. — An ultraviolet light that its sellers promise will "destroy swine flu virus." A dietary supplement claiming to be "more effective than the swine flu shot." Pills, hand sanitizers and air filters galore.

These products were among the hundreds of swine flu deterrents and cures that were advertised online this year. And their Internet purveyors were among the 80 who received warnings from the Food and Drug Administration over the past six months to stop peddling unproven or illegal treatments.

The FDA has issued an advisory, telling consumers to use "extreme care" when purchasing online products claiming to diagnose, treat or prevent the H1N1 virus. The agency and the Federal Trade Commission continue to closely watch these operations, anticipating more unauthorized items will pop up for sale as flu season draws near.

"It's very important that consumers know these products can be deceptive and risky," said Alyson L. Saben, deputy director of FDA's Office of Enforcement. "They offer a false sense of protection and could delay someone from seeking treatment."

Richard Cleland, the FTC's assistant director of the advertising practices division, said the SARS and anthrax scares generated similar products.

"Some marketers follow the news carefully ... and take advantage of people who are fearful," he said.

The majority of the warning letters, which tell companies to contact the FDA within 48 hours about their corrective plans or face enforcement action, involved dietary supplements, Saben said.

An array of products were cited: air and water filters, inhalers, kits including biohazard coveralls and plastic gloves.

Some online pharmaceutical retailers were offering Tamiflu, one of two antiviral drugs approved by the FDA for treating swine flu. The agency recently purchased and analyzed several of the products. One, which came in an envelope postmarked from India, consisted of two white tablets found to contain talc and acetaminophen but no oseltamivir, the active ingredient in Tamiflu.

Weil Lifestyle LLC, the online store featuring nationally known natural health guru Dr. Andrew Weil, was sent a warning Thursday regarding its vitamin packs and immune support formula.

In a written statement, Weil said the web site information was "primarily educational" and that his editorial content always is reviewed for federal law compliance. But he said the language that concerned the FDA had been removed and that he supported the agency's efforts.

FDA investigators found the suspect items through daily Internet searches, which they began shortly after federal health officials declared the H1N1 virus a public health emergency in April. Penalties for not correcting violations range from seizure of the products to criminal prosecution.

About 82 percent of the cited retailers have complied, Saben said, but enforcement actions are being considered against several who ignored the warnings.

Consumers can search for the warning letters at www.fda.gov. Click on "warning letters" on the right side.

Red flags for online shoppers include products that claim to treat multiple diseases or that claim to be scientific breakthroughs, and sites with personal or medical testimonials.