2014年经济学人 艾滋病 幽灵般的转机（在线收听）

HIV/AIDS

A spectre returns

The fall in HIV infections conceals a worrying rise among gay men

A TELEVISION campaign in the 1980s showed a volcano exploding and dark clouds looming over a blackened tombstone chiselled with the word AIDS. “Don't die of ignorance”, intoned a grim voice. Panic about the HIV/AIDS epidemic was widespread. Now better treatment, and better understanding of how the virus spreads, means that HIV is no longer a death sentence. But amid the good news there is cause for concern; among gay men in Britain infections are rising.

According to statistics released on November 18th by Public Health England (PHE), part of the NHS, 110,000 people in Britain were living with HIV in 2013, the highest number ever. But that is cause for celebration. Those infected are living much longer. People are being tested more often and diagnosed sooner. Between 2004 and 2013 new infections among heterosexuals fell by half.

Over the same period, however, the estimated annual number of new infections among men who have sex with men rose by a third, to 3,250. Some 13% of gay men in London are living with HIV. Compare that to San Francisco; the prevalence is higher—fairly static at about 24%—but the rate of new diagnoses is falling. In London, it is rising. This is partly explained by better testing. But reckless behaviour is also to blame.

“Chemsex”—taking drugs, especially crystal methamphetamine, GBL, or mephedrone, just before or during sex—is the chief innovation. Such drugs fuel sex binges, enabling people to have sex for longer, risking trauma and abrasion, and with a greater number of partners. Both increase the risk of transmission. The internet makes it easier to meet casual partners. David Stuart of 56 Dean Street, an NHS sexual-health clinic in Soho, says the centre sees around 100 gay men every month who use drugs for sex. Most have not had sober sex in six months, he says.

Cultural shifts may also be to blame. For some, fear of HIV may manifest itself in avoidance of the subject, via drugs and escapism, says Mr Stuart. But Amrou al-Kadhi, a magazine editor and drag performer, frets that others are in denial. Treatment has so improved that some assume they no longer need worry. He worries that some men treat post-exposure prophylactics like the morning-after pill. (Such medicine may stop infection if taken straight after exposure to HIV.) There is a divide, he suggests, between older gay men, who saw the horrors of the AIDS epidemic, and the young, who seem more complacent.

Analysis by Colin Brown, a research fellow at PHE, suggests that testing may not be as widespread as some believe. In 2011, 58% of gay men in Britain said they had been tested for HIV within the past year. But figures from sexual-health clinics in the capital suggest that 20% or less of HIV-negative gay men there get tested every year, half the rate in San Francisco. That city has seen a steeper decline in the proportion of those infected but unaware of it—who are most likely to infect others—than London has.

Better treatments leave campaigners with a dilemma. They want to see transmissions decline and promote behaviour that minimises risk. But they also want to reassure those who contract HIV that they can still live a long life. Some gay men appear to have taken the second message to heart at the expense of the first.