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How the climate crisis accelerates the global spread of deadly dengue fever



Images from Bangladesh show patients in hospital wards lying under mosquito nets, under beam electric lamps.

Mothers cool their babies from the sticky summer heat with hand fans while others rest on hospital floors holding drops,

Dengue is a seasonal mosquito-borne disease common in hot, humid areas of the tropics and subtropics through the rainy months.

Scientists say hotter, wetter weather created by climate change has created ideal conditions for female mosquitoes to lay their eggs. Not only are there more mosquitoes, but the rapid urbanization that has occurred in many Asian countries means that susceptible populations live in closer contact with the disease-carrying insects

Add to the mix inadequate or unprepared health services and the circulation of the virus and you have the ingredients for the outbreak of epidemic proportions ̵

1; and one that is likely to spread.

Bone Fever and Climate Crisis

Dengue is a virus infection transmitted by the Aedes mosquito, the same insect responsible for the spread of Zika, chikungunya and yellow fever. It causes flu-like symptoms, including headaches, muscle and joint pain, fever and rashes, although only 25% of those infected show symptoms. Extreme cases can lead to bleeding, shock, organ failure and potentially death.
It is the fastest spreading mosquito viral disease in the world, increasing 30 times in the last 50 years. Previously found in only nine countries, the disease is endemic in more than 100 today – putting more than half of the world's population at risk, according to the World Health Organization (WHO).
There are numerous studies on the link between climate change and mosquito-borne diseases, and experts say the climate crisis plays an important role in the spread of dengue.
Scientists have repeatedly warned that rising temperatures cause more extreme weather events and a warmer, humid world may put us at greater risk of diseases transmitted by – those transmitted by mosquitoes , ticks or other organisms. [19659016] Bangladeshi patients suffering from dengue fever rest on the floor of a hospital in Dhaka. "data-src-mini =" // cdn.cnn.com/cnnnext/dam/assets/190916163316-dengue-bangladesh-hospital-2-small-169.jpg "data-src-xsmall =" // cdn.cnn .com / cnnnext / dam / assets / 190916163316-dengue-bangladesh-hospital-2-medium-plus-169.jpg "data-src-small =" http://cdn.cnn.com/cnnnext/dam/assets/ 190916163316-dengue-bangladesh-hospital-2-large-169.jpg "data-src-medium =" // cdn.cnn.com/cnnnext/dam/assets/190916163316-dengue-bangladesh-hospital-2-exlarge-169 .jpg "data-src-large =" // cdn.cnn.com/cnnnext/dam/assets/190916163316-dengue-bangladesh-hospital-2-super-169.jpg "data-src-full16x9 =" // cdn .cnn.com / cnnnext / dam / assets / 190916163316-dengue-bangladesh-hospital-2-full-169.jpg "data-src-mini1x1 =" // cdn.cnn.com/cnnnext/dam/assets/190916163316- dengue-bangladesh-hospital-2-small-11.jpg "data-demand-load =" not-loaded "data-eq-pts =" mini: 0, xsmall: 221, small: 308, medium: 461, large: 781 "src =" data: image / gif; base64, R0lGODlhEAAJAJEAAAAAAP /////// wAAACH5BAEAAAIALAAAAAAQAAkAAAIKlI + py + 0Po5yUFQA7 "/>
A recent study suggests that 1 billion more people may be exposed to mosquito-borne disease by 2080 as temperatures continue to rise with the climate crisis.

Dengue-carrying mosquitoes thrive in urban areas and lay their eggs in shallow pools. water, in household containers, buckets, even inverted bottle caps. But environmental changes can affect how quickly viruses reproduce in mosquitoes and how long they live, increasing the risk to humans.

"With the increase in the average mosquito survival temperature and the actual replication of the mosquito pathogen, it becomes more effective," says Dr. Rabindra Aasinginghe, Coordinator of Malaria, Other Venous and Parasitic Diseases at the WHO Regional Office for West The Pacific ocean. "So mosquitoes need to survive only for shorter periods of time."

The unsuccessful time makes it difficult to predict outbreaks

Since the beginning of the year, more than 7 million people have been displaced worldwide as a result of disasters such as floods, cyclones and droughts – a phenomenon described by Inland Resettlement researchers as the norm.

"Climate change is changing meteorological models around the world. Seasonality is changing, we have less predictable extreme events," said Dr. Rachel Law of the London School of Hygiene and Tropical Medicine.

Law said these are changing models can lead to a change in the dengue season, "making it harder to know when and where an epidemic may occur."

2019 is also the year of El Nino, a warming weather phenomenon the atmosphere and changing patterns of circulation around the world – and usually rain South Asia is becoming unusually dry and experiencing droughts.
  How climate change will affect your health

Abeyasinghe said it was one thing to have an intense monsoon season where it rains constantly for several weeks, but quite another to have showers that "spread over several months, creating many mosquito breeding opportunities and prolonging survival mosquitoes as opposed to the short monsoon season. "

Neta warms, scientists say floating mosquito disease will continue to spread farther north. A recent study found that global warming caused by the climate crisis could see dengue-carrying mosquitoes Aedes aegypti – along with other diseases such as chikungunya, yellow fever and Zika – migrate to areas where it has not previously been endemic , Europe, the US, East Asia and parts of Central America, East Africa and Canada see large increases in risk. The modern way of life is also to blame

But climate is just one factor in the spread of dengue. We have been touring for more than 50 years and not only are we returning souvenirs from trips abroad.

"People can travel around the world in a matter of hours and this certainly facilitates the spread of dengue and can allow the virus to settle in places it has not been before," Low said.

Even global trade can contribute to allowing invasive mosquito species to settle in new places, as insects and their eggs can be transported in tires, transport containers and even boarded aircraft. . Some airlines, particularly in Australia and New Zealand, spray commercial aircraft to kill mosquitoes on board before leaving passengers.

  A municipal employee operates a fog machine to kill mosquito larvae to combat the spread of dengue in a village in Antipolo, Rizal province, east of Manila. A municipal employee operates a fog machine to kill mosquito larvae to combat the spread of dengue in a village in Antipolo, Rizal province, east of Manila.
The WHO said that the threat of a possible dengue epidemic now exists in Europe since the local transmission was first reported in France and Croatia in 2010, and import cases were detected in three other European countries. In October 2012, a dengue epidemic occurred in Madeira, Portugal, leading to over 2,000 cases in a country where the disease is not common.

A chorus is growing among experts, saying it is time for policymakers to begin preparing for the effects of climate change and its impact on the spread of infectious diseases.

"The extreme reality is that longer hot seasons will extend the seasonal window to the potential spread of vector-borne diseases and favor larger outbreaks," Dr. Giovanni Reza, Director of the Department of Infectious Diseases at Istituto The Superiore di Sanitá in Rome, Italy, said in a statement. "We must be prepared to deal with these tropical infections."

Reza said lessons should be drawn from West Nile virus outbreaks in North America and the Chikungunya in the Caribbean and Italy to "emphasize the importance of the assessment of future vector-borne disease. risks and preparing contingencies for future outbreaks. "

Stopping the Dengue Threat

  Field Officer Luu Quoc Hung of the World Mosquito Program Holds a Mosquito Bag in the Southern Vietnamese City of Nha Trang.
Without a reliable vaccine, the main form of mosquito prevention so far is mosquito control – through large-scale insecticide spraying, Dengue has become increasingly pesticide-resistant in several countries where it has once been was a successful tool to master
The four strains of the virus mean that it is difficult to overcome with effective treatment, but work is being done to eventually eliminate the disease.
The World Mosquito Control Program is an initiative with a nonprofit that uses naturally occurring bacteria to reduce mosquitoes' ability to transmit diseases like dengue.

It's called Wolbachia, and program scientists inject it into mosquito eggs to make them dengue resistant and then release eggs or fully grown coma

"In every country we work for, there is growing evidence that this seems to be a practical and effective way to stop dengue," says Peter Ryan, Director of Business Development for World Mosquito Program. "

When conducting field trials in 10 countries around the world, the team found that mosquitoes transmit the bacterium Valbachia from generation to generation – meaning that these mosquitoes do not transmit dengue.

The program was a success in northern Queensland, Australia, where the first tests were carried out in 2011.

"We have observed almost complete elimination of dengue from areas in northern Queensland, where we have now successfully implemented Wolbachia. These are 300,000 people living in areas that have been suffering from dengue almost every year since the 1980s and now we are seeing a complete collapse. "

Tests in Vietnam and Indonesia have also yielded positive results.

  Dengue fever: how a mosquito infects millions, not malaria

"The challenge is how to scale this quickly to make intervention accessible," Ryan said. Their goal is to reduce the cost of the program to about $ 1 for every person it helps so that it can be implemented in some of the poorest countries in the world. The field trials are expected to be completed in about 18 months.

Progress has also been made on the climate front. Lowe's team looks at how dengue countries can set up early warning systems to forecast future abnormal climates and help prepare for potential outbreaks.

"We can no longer rely on seasonal averages or averages to decide when dengue will peak," said Lowe.

"We need to think about how each place is connected to other endemic areas. We need to think about climatic conditions and unexpected extreme climatic events that can change the intensity of outbreaks."

Scientists find an affordable way to stop the spread of dengue, the WHO focuses on educating people about the disease – and preventing more deaths.

"What we encourage states to do is focus on better patient management," said Abesissinghe, "Because if you manage the patient and prevent death, what we really do is turn dengue into something like a normal flu-like thing. It's coming and going. "

Sandi Sidhu and Swati Gupta contributed to this report.


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