{"id":1187694,"date":"2023-08-23T08:30:00","date_gmt":"2023-08-23T08:30:00","guid":{"rendered":"https:\/\/grist.org\/?p=616541"},"modified":"2023-08-23T08:30:00","modified_gmt":"2023-08-23T08:30:00","slug":"dengue-fever-cases-surge-as-temperatures-rise","status":"publish","type":"post","link":"https:\/\/radiofree.asia\/2023\/08\/23\/dengue-fever-cases-surge-as-temperatures-rise\/","title":{"rendered":"Dengue fever cases surge as temperatures rise"},"content":{"rendered":"

This year, nearly 100,000 people<\/a> in Bangladesh have contracted dengue fever, a mosquito-borne viral disease common in tropical and subtropical regions of the world. The number of infected patients is overwhelming the fragile hospital system there. More than 450 people have died so far, the deadliest dengue outbreak<\/a> in the nation of approximately 170 million since record keeping began in 2000. Sri Lanka, nearby, is also experiencing a sharp spike \u2014 more than 40,000 cases<\/a> of dengue this year alone. <\/p>\n

Similar dengue-driven crises are unfolding in other parts of the globe. The Americas are in a \u201cpublic health emergency,\u201d according to the World Health Organization, or WHO: Peru experienced its largest dengue outbreak ever this summer<\/a>; Brazil, Bolivia, and Argentina are also reporting alarmingly high numbers of cases<\/a>. <\/p>\n

In the United States, five cases<\/a> of locally acquired dengue have been reported in Florida this month alone, prompting local health officials to put Miami-Dade and Broward counties on alert. The state has reported a total of 11 cases of locally transmitted dengue so far in 2023. <\/p>\n

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\"Workers
Workers from the Florida Keys’ mosquito-control department load a drone to spread BTI larvicide in an effort to eradicate dengue-carrying mosquitos on July 8, 2020, on Key Largo. Joe Raedle \/ Getty Images<\/cite><\/figcaption><\/div>\n<\/figure>\n

These outbreaks are concerning, but they\u2019re not particularly surprising to experts who have been tracking dengue for the past several decades. Cases of dengue \u2014 which can cause fever, rashes, vomiting, and, in severe instances, internal bleeding, organ failure, and death \u2014 have been rising for years. <\/p>\n

Since the beginning of the century, global cases of the disease, carried by the Aedes genus of mosquitoes, have skyrocketed, from roughly 500,000 in 2000 to more than 5 million <\/em>in 2019. In the first seven months of 2023, worldwide cases spiked to more than 3 million, and over 1,500 deaths <\/a>have been reported \u2014 numbers that are expected to rise as the summer continues. <\/p>\n

There are likely hundreds of millions more unreported incidents each year, as dengue produces mild or no symptoms in most people. But as more people get infected, the percentage who end up developing the severe form of the disease will increase, too. Experts say a tangled web of factors is driving the surge, but one culprit stands out: climate change.\u00a0<\/p>\n

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\"Dengue
Dengue patients, protected under mosquito nets, receive treatment at the Dengue Corner of Sylhet MAG Osmani Medical College & Hospital in Bangladesh. Md Rafayat Haque Khan \/ Eyepix Gr \/ Future Publishing via Getty Images<\/cite><\/figcaption><\/div>\n<\/figure>\n

In the 1970s, global cases of dengue fever, or break-bone fever as it\u2019s also commonly known, were low. Dengue had been more prevalent 20 years prior, but an aggressive campaign to eradicate Aedes aegypti mosquitoes using the now-banned insecticide dichlorodiphenyltrichloroethane, or DDT, lowered rates. The campaign was particularly successful in the Americas, where dengue and yellow fever, both carried by A. aegypti, were an omnipresent threat. <\/p>\n

But spraying DDT, a known carcinogen, into the environment quickly became an unsustainable mosquito-control measure. By the 1980s, as DDT was being phased out and a century of rampant fossil fuel use began to significantly influence the global climate, the disease began to spread again, and fast. In the next couple of decades, dengue would be found in 100 countries, up from just a handful of countries in the 1960s. Today, it\u2019s been detected in more than 140 nations. <\/p>\n

\u201cThis is the [mosquito-borne] disease that has grown most substantially in the past 10 years,\u201d Felipe J Col\u00f3n-Gonz\u00e1lez, a climate and health researcher who works at the global charitable foundation the Wellcome Trust, told Grist. \u201cThere are many factors that are related to climate.\u201d <\/p>\n

In order to gauge the influence of global warming on the spread of dengue, researchers look at three interconnected clues: where mosquitoes move, how quickly they develop, and how often they reproduce. <\/p>\n

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Like any creature on earth, mosquitoes thrive within a specific temperature range. The insects can\u2019t withstand temperatures that are too dry or cold. Anywhere below 57 degrees Fahrenheit, particularly when there\u2019s low humidity, is unlivable. But most mosquitoes can\u2019t withstand temperatures that are too wet or hot, either \u2014 large rainstorms wash them out and they tend to die off at 90 degrees F and above. <\/p>\n

Human industrial activity has warmed the planet by about 2 degrees F, on average, a seemingly small change that has had enormous implications for the spread of infectious disease \u2014 and life on earth writ large. <\/p>\n

Nepal, a mountainous country in South Asia, is a perfect example of how even a slight temperature change can open up a Pandora’s box of disease. Dengue wasn\u2019t present in Nepal until 2004, when the first case was recorded. Less than two decades later, in 2022, the country, which is warming more than 1 degree F every decade<\/a>, experienced its largest outbreak ever<\/a> \u2014 54,232 cases and 67 deaths. Researchers in Nepal noted that the nation\u2019s mountains are undergoing \u201cunusually large\u201d fluctuations in temperature. Snow cover on those mountains is melting away as climate change accelerates, inviting pests into new, higher territories. Afghanistan, also long considered too mountainous for Aedes mosquitoes, is witnessing a similar trend<\/a>. <\/p>\n

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A child infected with dengue at a hospital in Dhaka, Bangladesh, on August 14, 2023. Xinhua via Getty Images<\/cite><\/figcaption><\/div>\n<\/figure>\n

Climate change isn\u2019t just inspiring mosquitoes to move to higher elevations<\/a> \u2014 it\u2019s prompting the bugs to mature more quickly and produce more generations of offspring in a single season. <\/p>\n

Warmer temperatures increase both mosquitoes\u2019 rate of survival and development, and the rate at which they feed. Female mosquitoes, the ones that bite humans, digest blood more quickly when it’s warm and humid out. That leads to more disease. \u201cBecause the metabolism is faster, they have to feed many more times in a life cycle so there\u2019s more probability of an infection,\u201d said Col\u00f3n-Gonz\u00e1lez. <\/p>\n

Even temperatures that should be too hot for mosquitoes don\u2019t always kill them off. The insects hide in cool corners and under couch cushions to escape the heat, seeking shade much like humans do. \u201cMosquitoes are annoyingly intelligent creatures,\u201d Col\u00f3n-Gonz\u00e1lez said. <\/p>\n

It\u2019s clear that climate change is helping mosquitoes, and the diseases they carry, extend their reach across much of the planet. Roughly half the globe is now at risk for dengue, Raman Velayudhan, who leads the WHO\u2019s program for the control of neglected tropical diseases, said recently<\/a>. But mosquitoes are not invincible. Researchers have had success artificially infecting Aedes mosquitoes<\/a> with a bacterium that prevents the transmission of dengue from mosquitoes to humans. Pilot studies in South America and Southeast Asia have shown that the bacterium, called Wolbachia, can be incredibly effective: Cases of dengue in Yogyakarta, Indonesia, went down 77 percent<\/a> following the release of Wolbachia mosquitoes. <\/p>\n

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And other, more dependable and scalable methods of curbing dengue transmission exist. As is the case with many climate-driven illnesses, keeping communities safe from dengue ultimately comes down to resources and access. <\/p>\n

In the U.S., climate projections indicate that the atmospheric conditions for dengue will be ideal throughout much of the country<\/a> by the end of the century. But it\u2019s unlikely that dengue will become as widespread an issue as it is in underdeveloped countries. That\u2019s because most American homes have window screens that keep bugs out, and a large portion of the population has access to air conditioners that keep humidity low inside. Houses in the U.S. are spaced further apart than elsewhere in the world, which means a mosquito that breeds in one house won\u2019t necessarily bite people in the house next door. Americans also have widespread access to mosquito repellant. And in most areas, drinking water containers and sanitation systems are stored underground, which means mosquitoes can\u2019t breed in them. That\u2019s why in Texas, dengue is a rare disease while as many as 20 percent<\/a> of all dengue deaths in the Americas occur in Mexico. Two places that share a border and the same environmental conditions can have two completely different health outcomes. <\/p>\n

\u201cIt\u2019s true that the climate is going to become more suitable for dengue,\u201d Col\u00f3n-Gonz\u00e1lez said, pointing to rising temperatures and cases all over the globe. But the built environment, human behavior, and the quality of public health systems also play important roles \u2014 and point at potential silver linings that could help mitigate the dengue burden in countries with fewer resources. \u201cIt\u2019s not just the climate,\u201d he said.<\/p>\n

This story was originally published by Grist<\/a> with the headline Dengue fever cases surge as temperatures rise<\/a> on Aug 23, 2023.<\/p>\n","protected":false},"excerpt":{"rendered":"

Experts say a tangled web of factors is driving global spikes in dengue, but one culprit stands out: climate change.<\/p>\n","protected":false},"author":173,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/posts\/1187694"}],"collection":[{"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/users\/173"}],"replies":[{"embeddable":true,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/comments?post=1187694"}],"version-history":[{"count":2,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/posts\/1187694\/revisions"}],"predecessor-version":[{"id":1190118,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/posts\/1187694\/revisions\/1190118"}],"wp:attachment":[{"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/media?parent=1187694"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/categories?post=1187694"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/radiofree.asia\/wp-json\/wp\/v2\/tags?post=1187694"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}