Richard Knox

A lot of medicine's direst emergencies come down to one problem: lack of oxygen.

Cardiologist John Kheir started thinking about that when a little girl in his care, drowning from lung hemorrhages, died before she could be hooked up to a heart-lung machine that would have kept her blood oxygenated while the damage was repaired.

The Ebola virus continues to strike people in the Democratic Republic of Congo. Since May, the World Health Organization has counted 72 confirmed, probable or suspected cases and 32 deaths.

As usual, a disproportionate share of those cases are health care workers — 23 of them, almost a third.

The numbers for West Nile virus cases continue to rise, up 35 percent in the last week. But the Centers for Disease Control and Prevention is confident the nation has turned the corner on its worst-ever epidemic of West Nile virus disease.

Flu pandemics don't happen very often. So many people might feel the relative fizzle of a flu pandemic three years ago somehow immunizes the globe against another one for awhile.

But don't relax, say the authors of a report published online in the Proceedings of the National Academy of Sciences.

Cholera vaccine gives indirect protection to unvaccinated people in communities where a substantial fraction of the population gets the vaccine, a study in Africa shows.

The effect is called "herd immunity." It works because there are fewer bacteria circulating in communities where vaccination levels are relatively high.

Seventeen states offer tax incentives to people who donate a kidney, a portion of their liver or bone marrow for transplantation. But a study finds these sweeteners aren't working.

Researchers looked at what happened in the years before and after these tax incentives were passed and found no increase in organ donation rates.

Two Missouri farmers have been infected with a brand-new tick-borne virus that the Centers for Disease Control and Prevention is calling the Heartland virus.

The men recovered but suffered serious illness that required hospital care and weeks of convalescence. Symptoms included fever, severe fatigue, headache and nausea. Their platelet counts plummeted, but even though platelets are necessary for blood clotting, the men didn't suffer abnormal bleeding.

This year is on track to be the worst ever for West Nile virus in the United States. Here are the latest numbers from the Centers for Disease Control and Prevention:

• 1,590 reported cases, nearly 500 more than a week ago for a rise of 44 percent.
• 889 cases, or 56 percent, involve severe neurological disease.
• 66 deaths, compared to 41 last week.

Flu is most deadly for children with neurologic problems and disorders, an analysis of swine flu fatalities finds.

The results come from Centers for Disease Control and Prevention researchers who looked at childhood fatalities during the H1N1 flu pandemic of 2009, when there were five times the usual number of deaths.

In all, 43 percent of the deaths occurred in children who had neurologic diseases, such as cerebral palsy and epilepsy, or developmental disorders.

America's oldest citizens are generally getting healthier, living longer and doing better financially. But there's lots of room for improvement.

That's the take-home from an exhaustive picture of Americans over 65 put together by the federal government and released last week during the summer doldrums.

A month ago the results of a successful cholera vaccine project in Haiti became available. Now the World Health Organization is calling for the establishment of a global stockpile of the vaccine to respond to outbreaks like Haiti's.

Dr. Rochelle Walensky thinks the 19th International AIDS Conference will be remembered as the moment when the world began to mobilize to end the pandemic.

The Harvard researcher probably speaks for many of the 23,000 scientists, activists and policy mavens who came to the Washington conference. But they're going home with a big question on their minds: Can the world afford it?

The so-called Berlin patient is famously the only person in the world who has been cured of HIV. But he may soon have company.

Two people in Boston also seem to be free of HIV after undergoing bone marrow transplants for cancer, just as the Berlin patient did five years ago. The crucial difference is that the Boston patients have not yet stopped taking anti-HIV drugs — although that may happen in the coming months.

The big question hanging over the International AIDS Conference this week is whether all 34 million people in the world with HIV can possibly get antiviral drug treatment.

The HIV epidemic among African-Americans is getting deserved new attention at the 19th International AIDS Conference in Washington, D.C. And the news isn't all bad.

New data from the U.S. Centers for Disease Control and Prevention show that black high school students are engaging in risky sexual behavior far less often than they were 20 years ago.

Since black teens are the future of the epidemic for the hardest-hit ethnic group, this is encouraging.

Here are the main results:

There's a lot of buzz at the 19th International AIDS Conference about powerful new strategies to prevent HIV infection.

But a potent old strategy isn't used enough around the world, many researchers say, and is even neglected entirely in places where it's most urgently needed.

It's called needle exchange.

If you show up at the emergency department at San Francisco General Hospital — for any reason — there's a good chance they'll offer you an HIV test.

It's part of a big push, in a city closely associated with the AIDS pandemic, to find nearly all people infected with the virus and get them in treatment right away.

Ask AIDS researchers why they think a cure to the disease is possible and the first response is "the Berlin patient."

That patient is a wiry, 46-year-old American from Seattle named Timothy Ray Brown. He got a bone marrow transplant five years ago when he was living in Berlin.

The results are in on this spring's high-visibility pilot project to vaccinate 100,000 Haitians against cholera.

Almost 90 percent of the target population – half in Port-au-Prince and the other half in a remote rural area – got fully protected against cholera, meaning they got 2 doses of the oral vaccine.

The results defy the forecasts of skeptics who said in advance of the campaign that it would be lucky to protect 60 percent of the target populations.

There's something new to prevent HIV infections.

The Food and Drug Administration on Monday approved a once-a-day pill that can drastically lower a person's risk of getting the virus that causes AIDS.

It's called Truvada — the first HIV prevention pill.

It's not cheap — around $13,000 a year — and it's not clear what insurers will pay for it. And there's worry that people taking the pill might relax safe-sex precautions.