Everyone knows that urban legends spread like…well, viruses. (Remember the one about  crocodiles in the subway?) But judging from the terror tales that clogged the Internet in March, legends about viruses are in a category of their own. First to fly over the wires was one about HIV-infected syringes in pay-phone change slots. Then another mass e-mailing warned: “Check your chairs when going to the movie theater!! An incident occurred recently in Dallas when a woman sat in a theater and something poked her. She got up and found a needle with a note attached: ‘Welcome to the real world—you’re HIV positive.’” The e-mails claim falsely to come from police in Dallas and Virginia and report that the Centers for Disease Control (CDC) “is aware of similar events in several cities.” The rumors’ kicker? “All the needles tested have been positive for HIV.”

After its hotline received an avalanche of calls, the CDC set up a webpage (www.cdc.gov/nchstp/hiv aids/pubs/faq5a.htm) to debunk the rumors. Though it confirmed that one Virginian had been pricked by a needle in a pay phone and that another syringe was found in a vending machine, it stated: “Reports have falsely indicated that the CDC confirmed the presence of HIV in the needles. The CDC has not tested such needles. The majority of these warnings appear to have no foundation in fact.”

On the syringe tip, Dr. Nadia Abdala and her colleagues at Yale University recently asked a pointed question: How long can HIV survive in needles? Four weeks was their answer, published in January’s Journal of Immune Deficiency Syndromes. Since HIV thrives in moist solutions—and deactivates when it dries out—airtight syringes are prime for viral survival, Abdala said.

The study bolsters the case for syringe swaps, which have been found to cut needle circulation time from three weeks to three days. Nevertheless, Abdala said, “Since the government’s decision not to fund needle exchange is political, not scientific, we can’t tell what effect it will have.”