BANGKOK — Nearly all of the world’s 35,000 online pharmacies are being run illegally and consumers who use them risk getting ineffective or dangerous drugs, according to the U.S. Trade Representative’s annual report on “notorious markets.” The report also singled out 19 countries over concerns about counterfeit or pirated products.

The report also named about three dozen online retailers, many of them in China or elsewhere in Asia, that it said are allegedly engaged in selling counterfeit products or other illegal activities.

The report says 96% of online pharmacies were found to be violating the law, many operating without a license and selling medicines without prescriptions and safety warnings.

Their websites often look like legitimate e-commerce platforms, often with false claims that they are approved by the Food and Drug Administration, said the report, released Wednesday. The FDA and U.S. Drug Enforcement Administration have both issued warnings about risks of buying prescription medicines from such sources.

It cited a survey by the Alliance for Safe Online Pharmacies’ Global Foundation that found nearly 1 in 4 Americans who have used online pharmacies reported having encountered substandard, fake or harmful medicines.

Last year, Federal prosecutors reported that a network of illegal drug sellers based in the U.S., the Dominican Republic and India had packaged potentially deadly synthetic opioids into pills disguised as common prescription drugs and sold millions of them through fake online drugstores, federal prosecutors said Monday. At least nine people died of narcotics poisoning between August 2023 and June 2024 after consuming the counterfeit pills, the indictment said.

Apart from the risks of using drugs that may contain inert ingredients or could cause allergies, the medicines are sometimes made in unsanitary conditions, the report said.

The USTR’s annual report cited examples from within the United States, but also mentioned risks of imported ingredients including fentanyl from China. Many of the illicit online pharmacies are based outside the U.S.

The Notorious Markets List did laud progress in fighting counterfeit and pirated goods.

But problems remain with cyberlockers that thwart efforts to restrict piracy of movies and other content and of so-called “bulletproof” internet service providers that promise users leeway for using pirate sites, it said.

One such ISP is Avito, a Russian-based ad platform that allegedly lets sellers advertise counterfeit products.

While a large share of theft of intellectual property has moved online, the report also highlighted real-world locations notorious for selling counterfeit products, including markets in Turkey, bazaars in the United Arab Emirates and Saigon Square Shopping Mall in Vietnam’s Ho Chi Minh City.