Climate Change May Affect Dengue and Malaria Disease Risks
2020-09-21
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1The future may mean more dengue and less malaria in parts of Africa if the planet continues to warm, a new study says.
2Humans contract the diseases through mosquito bites.
3The Anopheles mosquito carries a parasite that causes malaria.
4Dengue is caused by a virus carried by the Aedes mosquito.
5These two mosquitos also do best in different climates.
6Malaria mosquitos thrive in temperatures of about 25 degrees Celsius.
7Dengue mosquitos like it hotter, by about 4 degrees.
8Erin Mordecai is assistant professor of biology at Stanford University in California.
9She is the lead writer of the study.
10Mordecai said climate change may weaken the spread of malaria but increase the spread of dengue.
11Combining mosquito temperature data, population numbers, and climate expectations, the researchers predicted malaria and dengue risks for Africa.
12The dengue mosquito is expected to spread across sub-Saharan Africa fully by 2080.
13And a resulting rise in dengue cases is not the only worry.
14Aedes mosquitoes can also carry chikungunya, Zika and yellow fever viruses.
15At the same time, the researchers say, malaria risk will drop as Anopheles mosquitos move further south and into mountainous areas seeking cooler temperatures.
16The researchers say that the growth of cities in Africa may further increase the risk of dengue.
17The Aedes mosquito reproduces in very small, often human-made, containers, like bottle covers.
18Such environments are more commonly found in cities, said Mordecai.
19The Anopheles mosquito lays its eggs in larger, natural bodies of water, like lakes and rivers.
20Cities are usually also warmer than surrounding rural areas - a better environment for the heat-loving Aedes.
21"We're predicting that dengue is going to become a much bigger problem in Africa," said Desiree LaBeaud, who helped write the study.
22She is an expert on infectious diseases in children at Stanford University.
23Africa is probably not well-prepared to fight dengue, she said.
24It has fought the spread of malaria with some success, but dengue will require new preventative measures.
25And, Mordecai says, tools for identifying dengue disease are not widely available on many parts of the continent.
26Generations of scientists and technicians have had training and experience in controlling malaria mosquitoes.
27But the dengue mosquito is a "very different creature and a different enemy," says Philip McCall, a researcher at Liverpool School of Tropical Medicine in the United Kingdom.
28He was not involved in the study.
29McCall notes other studies have shown links between climate change and dengue.
30"It's more likely you would have an increase in dengue, or possibly chikungunya and Zika," growing into a serious problem in cities, he said.
31"But I can't see malaria, which is so established in Africa, disappearing easily. So it could become like double-trouble," he added.
32Joacim Rocklöv is professor of epidemiology at Umeå University in Sweden.
33He was not involved in the Stanford study.
34But he points out that it is limited.
35It only considers a "very fossil fuel-intensive future, which some people think is a little bit unlikely," he said.
36If you change those projections, he added, "then you might see quite different results" in connection to malaria.
37The best way to control dengue is by removing containers that hold still water.
38This gives the mosquitoes fewer places to reproduce.
39Another way is to make sure containers are fitted with tight covers.
40But there is also new hope for a different kind of dengue control.
41A natural bacterium called Wolbachia blocks the dengue virus from reproducing in the mosquito and prevents spread.
42A trial involving release of Wolbachia-infected mosquitoes in Indonesia was found to reduce dengue cases.
43These mosquitoes have reduced the spread in a huge area of Yogyakarta by 77 percent, "which is incredible," said McCall.
44I'm Alice Bryant.
1The future may mean more dengue and less malaria in parts of Africa if the planet continues to warm, a new study says. 2Humans contract the diseases through mosquito bites. 3The Anopheles mosquito carries a parasite that causes malaria. Dengue is caused by a virus carried by the Aedes mosquito. 4These two mosquitos also do best in different climates. Malaria mosquitos thrive in temperatures of about 25 degrees Celsius. Dengue mosquitos like it hotter, by about 4 degrees. 5Erin Mordecai is assistant professor of biology at Stanford University in California. She is the lead writer of the study. Mordecai said climate change may weaken the spread of malaria but increase the spread of dengue. 6Combining mosquito temperature data, population numbers, and climate expectations, the researchers predicted malaria and dengue risks for Africa. 7The dengue mosquito is expected to spread across sub-Saharan Africa fully by 2080. And a resulting rise in dengue cases is not the only worry. Aedes mosquitoes can also carry chikungunya, Zika and yellow fever viruses. 8At the same time, the researchers say, malaria risk will drop as Anopheles mosquitos move further south and into mountainous areas seeking cooler temperatures. 9The researchers say that the growth of cities in Africa may further increase the risk of dengue. The Aedes mosquito reproduces in very small, often human-made, containers, like bottle covers. Such environments are more commonly found in cities, said Mordecai. The Anopheles mosquito lays its eggs in larger, natural bodies of water, like lakes and rivers. 10Cities are usually also warmer than surrounding rural areas - a better environment for the heat-loving Aedes. 11"We're predicting that dengue is going to become a much bigger problem in Africa," said Desiree LaBeaud, who helped write the study. She is an expert on infectious diseases in children at Stanford University. 12Africa is probably not well-prepared to fight dengue, she said. It has fought the spread of malaria with some success, but dengue will require new preventative measures. 13And, Mordecai says, tools for identifying dengue disease are not widely available on many parts of the continent. 14Generations of scientists and technicians have had training and experience in controlling malaria mosquitoes. But the dengue mosquito is a "very different creature and a different enemy," says Philip McCall, a researcher at Liverpool School of Tropical Medicine in the United Kingdom. He was not involved in the study. 15McCall notes other studies have shown links between climate change and dengue. 16"It's more likely you would have an increase in dengue, or possibly chikungunya and Zika," growing into a serious problem in cities, he said. 17"But I can't see malaria, which is so established in Africa, disappearing easily. So it could become like double-trouble," he added. 18Joacim Rocklöv is professor of epidemiology at Umeå University in Sweden. He was not involved in the Stanford study. But he points out that it is limited. It only considers a "very fossil fuel-intensive future, which some people think is a little bit unlikely," he said. If you change those projections, he added, "then you might see quite different results" in connection to malaria. 19The best way to control dengue is by removing containers that hold still water. This gives the mosquitoes fewer places to reproduce. Another way is to make sure containers are fitted with tight covers. 20But there is also new hope for a different kind of dengue control. 21A natural bacterium called Wolbachia blocks the dengue virus from reproducing in the mosquito and prevents spread. A trial involving release of Wolbachia-infected mosquitoes in Indonesia was found to reduce dengue cases. 22These mosquitoes have reduced the spread in a huge area of Yogyakarta by 77 percent, "which is incredible," said McCall. 23I'm Alice Bryant. 24Asher Jones reported this story for VOA News. Alice Bryant adapted it for Learning English. Caty Weaver was the editor. 25________________________________________________________________ 26Words in This Story 27mosquito - n. a small, flying insect that bites the skin of people and animals and sucks their blood 28parasite - n. an animal or plant that lives in or on another animal or plant and gets food or protection from it 29assistant - n. a person who helps someone 30data - n. facts or information used usually to calculate, analyze, or plan something 31sub-Saharan - adj. the area of Africa that is south of the Sahara Desert 32epidemiology - n. the study of how disease spreads and can be controlled