盖茨基金会继续抗击结核病

WASHINGTON — By Abigail Martin

Tuberculosis, or TB, is spread when an infected person coughs or sneezes, dispersing the germ—mycobacterium TB—into the air. The World Health Organization says there were an estimated 8.7 million new cases of TB in 2011. Nearly all TB cases are found in low and middle income countries. People infected with HIV, the AIDS virus, are especially vulnerable because of their weakened immune systems.

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TB is a difficult disease to treat because some strains of the bacterium have developed a resistance to drugs. But Dr. Peter Small, of the Bill and Melinda Gates Foundation, is impressed by recent research developments.

“There were probably forty years in which there was very little, arguably no, progress because there was no effort,” he explained. “What we’ve seen in the last decade is an acceleration. And it’s really changed what was a vicious cycle of neglect and despondency into one in which we’re starting to see exciting new products. We have now, for the first time, the capacity for untrained healthcare workers to definitively diagnose TB within two hours and know if it’s drug resistant. More than two and a half million of those tests run in the world.”

Small is the Gates Foundation’s senior program officer for TB. He has researched the genetic variability of the disease and has seen the effects of TB firsthand while living in India.

He says it’s important to determine which drug combinations provide the best treatment. Small says streamlining approval of effective drug regimens allows those who are infected to receive treatment sooner. But drugs are not the ultimate solution when addressing TB.

“I think the Holy Grail remains a vaccine,” Small said. “We do need a vaccine to finish the job. The great thing is that we’ve completed a phase three trial. We’ve shown that we can get definitive answers and unfortunately that trial was ineffective. But I think that the vaccine pipeline is now something which we know we can test. The good news is, in the last fifteen years there have been massive improvements in understanding immunology.”

As the world awaits a vaccine, research continues on new drugs that could be effective against multidrug-resistant and extensively drug-resistant types of TB.

Small explained, “These are agents that attack bugs in ways that they’ve never seen before so that the so-called multi-drug resistant is essentially no different than susceptible TB. Because these are new agents, they work new ways. And there are a number of promising ones in the pipeline. Taking some of those and putting those together would mean that you have a new regimen which treats everyone, drug-susceptible or drug-resistant.”

Drug-resistant strains of TB develop through the improper use of medication. If the drugs are taken incorrectly—such as missing doses—they become ineffective because the bacterium develops resistance.

Multidrug-resistant TB is on the rise, particularly in children. But finding the children who need treatment is not easy.

“It’s actually very difficult to diagnose TB in children because we generally think of TB as pneumonia,” Small said. “And we get pneumonia samples by having people cough and spit. And you can’t get five year olds and below to cough and spit. Because we can’t diagnose it, the world has tended to assume it doesn’t exist. And because they assume it doesn’t exist, then they don’t feel the need to invest in diagnosing it. When you can diagnose TB with a blood sample, it’ll be a lot easier to diagnose TB in kids.”

Treating the millions of children and adults infected with TB may seem daunting. However, the fact that the TB mortality rate has decreased 41% since 1990 gives hope for future progress and elimination of the disease.