VOA标准英语2010年-In Cameroon, TB Vaccine Breakthrough E

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Deaths from tuberculosis¹ are increasing in the developing world and especially in Africa. It's the world's second deadliest infectious disease after HIV/AIDS. In 2008, nearly two million people died of TB and researchers warn that mortality rates will surge further if new drugs and vaccines³ are not developed.
Linda is a 35-year-old Cameroonian mother of two. She's one of 35.000 people in the country diagnosed every year with tuberculosis, which kills some 7,000. Her problem is compounded by the fact that she's also infected with HIV, the virus that causes AIDS:
X-ray of patient with tuberculosis"It is very difficult," she said. "Several times, I consider suicide but then I think about my children and want to be there for them. I have had TB for several years and despite all the drugs, I am still ill. The doctor says my problem is severe because I also have HIV. I have to take countless⁴ numbers of medicines every day and sometimes I just can't stand it."Like others in her condition, Linda longs for the day when an effective remedy will be found.
In early October, more than 200 researchers met for an international symposium⁵ in the Cameroonian capital, Yaounde. They discussed the disease, but had no new drugs or vaccines to report. They could only talk about new ways to improve existing treatments.
The meeting was hosted by the Novartis Institute for Tropical Diseases, a non-profit research organization trying to find new medicines for the treatment of neglected, infectious diseases like TB, malaria⁶ and Dengue fever.
One of the conference participants, Prof. Barry Clifton of the US National Institutes of Health, says the absence of new drugs is steadily⁷ increasing the number of deaths from TB:
"I don't feel very optimistic about a breakthrough any time in the foreseeable future unless people put more effort and emphasis and research into tackling TB," he said. "At our current level, I think we'll keep the pace to the point where we hopefully don't have many people who don't have any options. But we're not going to win the race."The only available vaccine² for TB, known as Bacille-Calmette-Guerin (BCG) was developed almost 90 years ago. It's a live vaccine similar to the TB bacterium⁸ and has been improved over the years to provide immunity⁹ with the first dose.
But while it reduces risks of severe forms of TB in early childhood, it is not very effective in adults, who can be infected even if they were vaccinated¹⁰ in their youth. And BCG is not safe for children with HIV because it can spur the onset¹¹ of the disease in those with weakened immune systems. Across Africa, most children are given the vaccine without knowledge of their HIV status.
The Link Between HIV and TBProf. Paul Herrling is head of the Novartis Institutes for Developing World Medical Research. He says there are a number of reasons for the current dilemma¹²:
"The first one is that the last medicines that we had for TB are about 40 years old, and one thing that people did not know at that time is that this is a very clever bacterium and when they're treated with the same medicines for a long time, they learn to escape it. That's what we call resistance."Scientists say TB strains can vary from multi-drug resistant¹³ (MDR-TB) to extensively drug resistant (XDR-TB).
The most prominent way the TB virus gains resistance is in patients' failing to complete their treatments.
Researchers say fighting tuberculosis is made more difficult by the increasing number of people, especially in Africa, like Linda, who are also infected with HIV. Prof. Christopher Kuaban of the University of Yaounde in Cameroon says HIV/AIDS patients are up to 20 times more likely to develop TB than people without HIV:
"HIV is an infection that destroys your immune system. TB is contained by this immune system – so if your immune system breaks down when you're infected by TB, the TB germ has nothing to fear because there's nobody to destroy it. That's why in any country where HIV is common, TB becomes very common."Ongoing¹⁴ research inconclusiveCurrent treatment is cumbersome¹⁵: it takes six to nine months and patients must take several tablets several times a day. Research in several parts of the world is focusing on developing treatment that's easier for the patient, as well as vaccines that may replace BCG.
Clinical trials are about to begin on one vaccine candidate -- called AERAS-422. They will be conducted in Kenya, South Africa, Uganda and India by the non-profit research organization Aeras Global TB Vaccine Foundation. It recently obtained a $785,000 three-year-grant from the US Food and Drug Administration. Officials say the results may be available by the year 2020.
Funding is a problem say researchers like Barry Clifton:
"A normal pharmaceutical¹⁶ company will take a hundred people working for several years to get a candidate to put into clinical trials. With TB, we don't have those kinds of resources because it's a developing world disease, and there's no financial incentive¹⁷. So, we try to do the best we can with the small resources we have. It's market-driven, so the big pharmaceutical companies are responsible for making money [for their shareholders]."Meantime, the epidemic¹⁸ continues to grow, especially in Africa, where cities are increasingly crowded; where poor people find little to eat to bolster¹⁹ their immune systems and where healthcare services are not adequate.
As a result, more and more people like Linda and her children are victims of stigma²⁰ and discrimination. They are increasingly turning their backs on hospitals and heading for traditional healers and proliferating²¹ prayer churches for help.
TB's Intimidating²² ComplexitiesTB is caused by a bacterium known as the Mycobacterium tuberculosis. It's spread from person to person through tiny airborne droplets²³ of infected sputum. It can affect almost any tissue or organ in the body, with the most common site being the lungs. Basically, it cripples the human immune system, leaving patients vulnerable to deadly bacterial²⁴ infection.
The WHO says of the nine million people diagnosed with TB worldwide last year, a third live in Africa. It's currently the leading cause of death among people with HIV/AIDS on the continent.