VOA常速英語: 研究：被誤認為瘧疾的疾病

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A new study warns that, in Africa, illnesses causing fevers are often misdiagnosed as malaria. For example, the study found that dengue fever is circulating in urban areas of Ghana, but is mistaken for malaria. The findings could trigger a reevaluation of anti-malaria efforts.

Dengue fever is caused by a virus transmitted through a mosquito bite. It’s a flu-like illness that a fatality rate of about five percent. The World Health Organization said there’s no specific treatment, but early detection and proper medical care can sharply reduce the risk of death. While the death toll may be low, dengue has hindered development in parts of the world.

The study’s lead investigator, Justin Stoler, has studied dengue fever and malaria for many years in Latin America. But while doing research in Ghana he wondered whether dengue and other febrile diseases ever had been considered a big problem?

“I had always noticed that the urban ecology – the types of breeding environments that certain mosquitoes like – all existed in West Africa. And yet these diseases were generally off physicians’ radar. And many years ago I sat in a symposium with [the] Ghana Medical Society and they were talking about the high malaria rates. And I asked, I said, ‘Have you looked at other viral fevers, other types of diseases that are circulating everywhere else in the tropics?’ And I was roundly shook off. And I thought to myself, well, someone needs to look into this stuff.”

Stoler is assistant professor of geography at the University of Miami College of Arts and Sciences. He said the study is the first to show that dengue and other fever-causing diseases are circulating in Ghana. In fact, he said, “Many diseases with classic fever and headache symptoms that are circulating are being misdiagnosed on a massive scale.”

“The best data we have is from Accra, Ghana’s capital. And we see there roughly 40 to 45 percent of all outpatient visits – anyone presenting at a hospital, a healthcare facility – for any reason – are walking out of there with a presumptive malaria diagnosis, which is a staggering number in and of itself. Now, what we’re just starting to learn in the last few years is that when you actually do confirmatory blood tests -- and you look at who really has malaria -- typically it’s less than 10 percent of that group, who’s presumed to have malaria,” he said.

So, if those figures are correct, what diseases could the rest actually have?

“Well, we started with dengue because it’s widespread across the tropics. It’s recognized. It’s something many people have heard of. But in reality it’s probably just a small piece of the pie. There are bacterial infections, other viral fevers, viral infections – things like influenza – fungal diseases, other parasitic infections…really a whole menu of things that people are dealing with on a regular basis,” said Stoler.

Many of the diseases are water related and infections can increase during the rainy season or floods. It’s not just malaria mosquitoes that breed in these conditions.

He said, “When you see spikes in people rushing to the hospitals and the clinics after the rainy season, again, this is part of the reason why we have this institutionalized view that after the rainy season you seek spikes in fevers. Therefore, it is all malaria. But it’s actually all these other diseases that have very similar links in ecologies.”

Stoler said the findings have the potential to cause donors to re-think their anti-malaria strategies. The Roll Back Malaria Global Action Plan estimates nearly $6 billion a year is spent to fight malaria.

“At least in parts of rapidly urbanizing Africa, maybe malaria is not their biggest problem. I don’t mean to undermine the importance of fighting malaria in sub-Saharan Africa and around the world, in general. But malaria has traditionally been a rural disease and that’s probably still where most of the burden exists. But really all the action is in urban places and there a lot of other things that people are dealing with there,” he said.

Since dengue is spread by mosquitoes, would anti-malarial bed nets help to reduce infections?

“Well, that’s what’s interesting,” said Stoler, “There’s some evidence that in certain parts of sub-Saharan Africa that the Aedes mosquitoes that spread dengue fever – also are mosquitoes responsible for spreading Chikungunya and Yellow Fever, by the way. These mosquitoes tend to be active at dawn and dusk. And so, using mosquito nets you may get a little bit of protection in the early morning hours. But the reality is that these mosquitoes do bite throughout the day and that traditional interventions, like bed nets, are not going to be effective in getting the vast reductions in morbidity and mortality that we see with malaria control.”

Stoler said the findings should be presented to various medical societies for consideration. He also says health care workers should be trained to look for other, lesser known infections.

The University of Miami assitant professor says the findings can also play a role in the writing of the Sustainable Development Goals. They’ll replace the Millennium Development Goals at the end of this year.

The study appears in the American Journal of Tropical Medicine and Hygiene.