Richard Knox

A vaccine against human papillomavirus — the most common sexually transmitted infection and the cause of almost all cervical cancer — is dramatically reducing the prevalence of HPV in teenage girls.

The first vaccine against HPV, Merck's Gardasil, was approved by the Food and Drug Administration in 2006. Cerverix, from GlaxoSmithKline, was approved in 2009.

A once-a-day pill has been proven to lower the risk of getting HIV among needle-using drug addicts, just as it does among heterosexual couples and men who have sex with men.

Among 2,400 injecting drug users in Bangkok, those assigned to take a daily dose of an antiviral drug Viread, or tenofovir generically, had half the risk of getting HIV over a four-year period as those who took a placebo pill. Among those who took tenofovir faithfully, there were 74 percent fewer infections.

The World Health Organization is warning health care workers everywhere to suspect a disease called Middle Eastern Respiratory Syndrome, or MERS, whenever they see a case of unexplained pneumonia.

Monday's warning comes at the end of a six-day WHO investigation in Saudi Arabia, where 40 of the 55 cases of the respiratory disease have occurred. Sixty percent of those people with known infections died.

The chief of the National Institutes of Health is disavowing a ruling from the government office that oversees the ethics of human research.

Every day in hospitals all over America, thousands of patients die of infections that used to be curable. But the antibiotics used to treat them aren't working anymore.

It's called drug resistance, and it's largely a consequence of antibiotics overuse. The more germs are exposed to antibiotics, the faster they mutate to evade being vanquished.

Thanks to gold-standard tuberculosis treatment and prevention programs, cases of TB in the United States have declined every year for the past two decades — to the lowest level ever.

But TB's course through the Williams family in Boston shows that no nation can afford to relax its efforts to find, treat and prevent TB. It's just too sneaky and stubborn an adversary.

Most women diagnosed with breast cancer when they're 40 or younger are choosing mastectomy rather than more limited and breast-conserving lumpectomy plus radiation, a study of women in Massachusetts finds.

Moreover, most of those choosing mastectomy elect to have the other, noncancerous breast removed, too.

Scientists have completed the first assessments of how readily the H7N9 flu virus in China can pass among ferrets and pigs. The mammals provide the best inkling of how dangerous these bugs may become for humans.

The news is both bad and good. They've found the new bird virus is easily passed between ferrets sharing the same cage.

It's been eight months since a Saudi Arabian doctor described a previously unknown virus related to SARS. And for most of that time only germ geeks paid much attention.

But in the past few days the new virus — which some would like to call MERS-CoV, for Middle East Respiratory Syndrome Coronavirus — has been making up for lost time.

There's been a buzz of activity at the Centers for Disease Control and Prevention in Atlanta since scientists got their first samples of a new bird flu virus from China four weeks ago.

Already they've prepared "seed strains" of the virus, called H7N9, and distributed them to vaccine manufacturers so the companies can grow them up and make them into experimental flu vaccine.