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How the climate crisis is accelerating the worldwide spread of fatal dengue fever



Images from Bangladesh show patients in overcrowded infirmaries lying under mosquito nets under glaring electric light bands.

Mothers cool their children from the sticky summer heat with hand fans, while others rest on hospital floors and hold drops. Waiting for a free bed.

Dengue fever is a seasonal, mosquito-borne disease that commonly occurs in hot, humid regions of the tropics and subtropics during the rainy months.

Scientists claim that hotter, wetter weather is the cause Climate change has created ideal conditions for female mosquitoes to lay their eggs. Not only are there more mosquitoes, but rapid urbanization in many Asian countries also causes vulnerable populations to live in closer contact with disease-carrying insects.

Add to Mix inadequate or unprepared health services and the spread of a virus, and you have the ingredients for an outbreak of epidemic proportions ̵

1; and one that is likely to spread.

The Break-Bone Fever and the Climate Crisis

Dengue is a virus infection caused by the Aedes mosquito, which is responsible for the spread of Zika, Chikungunya and Yellow Fever. It causes flu-like symptoms, including pervasive headaches, muscle and joint pains, fever, and rashes, although only 25% of those infected show symptoms. Extreme cases can cause bleeding, shock, organ failure and possibly death.
It is the world's fastest-growing mosquito-borne viral disease, which has increased 30-fold in the last 50 years. Once found in only nine countries, the disease is now endemic in more than 100 countries – according to the World Health Organization (WHO), more than half of the world's population is at risk.
There have been numerous studies on the relationship between climate change and mosquito-borne diseases, and experts say that the climate crisis plays an important role in the spread of dengue.
Scientists have repeatedly warned that rising temperatures trigger more extreme weather events and that a warmer, wetter world could present a higher risk of vector-borne diseases – those transmitted by mosquitoes, ticks or other organisms. [19659016] Bangladeshi patients with dengue fever are resting on the floor of an infirmary in Dkaha. "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, R0lGODlhEAAJEAAAAAP /////// wAAACH5BAEAAAIALAAAAAQAAkAAAIKlI + py + 0Po5yUFQA7 "/>
A recent study suggested that by 2080, 1 billion people may be exposed to a mosquito-borne disease as temperatures continue to rise with the climate crisis.

Dengue-bearing mosquitoes thrive in urban areas and drain their eggs in shallow basins from water, in household containers, buckets, even upside-down bottle caps. But environmental changes can affect how quickly viruses multiply in mosquitoes and how long they live, which increases the risk to humans.

"As the average temperature increases, the survival of mosquitoes and the actual replication of the mosquito pathogen becomes more efficient," Dr. Rabindra Abeyasinghe, Coordinator for Malaria, other vector-related and parasitic diseases at the WHO Regional Office for the Western Pacific. "The mosquitoes have to survive only a short time."

Irregular weather makes forecasting outbreaks more difficult

Since the beginning of the year, more than 7 million people worldwide have been displaced by disasters such as floods, hurricanes and droughts – a phenomenon described as normal by researchers of Internal Displacement ,

"Climate change is changing weather patterns around the world, seasons are changing, we have less predictable extreme events," Dr. Rachel Lowe from the London School of Hygiene and Tropical Medicine.

Lowe said that these changing patterns may cause the dengue season to shift "making it harder to know when and where an epidemic could occur".

2019 is also an El Nino year, a weather phenomenon that warms the atmosphere and changes circulation patterns around the globe – and the typically rainy South Asia is unusually dry and suffers from drought.
  How will climate change affect you? Health

Abeyasinghe said it was one thing to have an intense monsoon season in which it would last for several weeks It is raining steadily, but having very different showers that are "scattered over several months, creating a variety of opportunities for mosquito breeding and prolonging the survival of mosquitoes as opposed to a brief monsoon season".

As the planet gets warmer, scientists say, mosquitoes will infect them. Diseases will continue to spread northward. A recent study found that rising temperatures around the world could cause the female Aedes Aegypti mosquito carrying dengue fever, along with other diseases such as Chikungunya, Yellow Fever and Zika, to migrate to areas where it has not previously In Europe, the USA, East Asia and parts of Central America, East Africa and Canada, the risk is high.

Even modern lifestyles are to blame.

However, the climate is only one factor in the spread of dengue. We travel a lot more than 50 years ago and not only bring souvenirs from foreign travel.

"People are able to travel around the globe in a matter of hours, which certainly favors the spread of dengue fever and allows the virus to establish itself in places it was not before," said Lowe can help move invasive mosquitoes to new locations, as insects and their eggs can be transported in tires, shipping containers and even transported by airplanes. Some airlines, especially in Australia and New Zealand, spray commercial airliners to kill mosquitoes on board before passengers get off.

  An urban employee operates a fog machine to kill mosquito larvae to fight the spread of dengue in a village in the city Antipolo, Rizal province, east of Manila.
The WHO The danger of a possible dengue outbreak now exists in Europe, as in 2010 for the first time local transfers were reported in France and Croatia and in three other European countries import cases were found. In October 2012, a dengue outbreak in Madeira, Portugal, resulted in more than 2,000 cases in a country where the disease does not normally occur.

Experts say it is time for policy makers to prepare for the impact of climate change and its impact on the spread of infectious diseases.

"The terrible reality is that longer hot seasons increase the seasonal window for the possible spread of vector-borne diseases and promote larger outbreaks," Dr. Giovanni Rezza, director of the Department of Infectious Diseases at the Istituto Superiore di Sanitá in Rome, said in a statement. "We have to be prepared to deal with these tropical infections."

Rezza said lessons should be learned from the outbreaks of the West Nile virus in North America and Chikungunya in the Caribbean and Italy to highlight the importance of assessing future vector-borne diseases risks and preparing contingencies for future outbreaks ,

Stop Dengue Fever

  Field officer Luu Quoc, who is suspended from the World Mosquito Program, holds a bag of mosquitoes in the southern Vietnamese city of Nha Trang.
Without a reliable vaccine, the most important form of disease prevention to date has been mosquito control – by spraying insecticides over large areas – but Dengue fever has spread to several countries a successful disease-control agent resistant to pesticides.
The four strains of the virus make it difficult to keep up with effective treatments, but work is in progress to eradicate the disease.
The World Mosquito Program is a nonprofit initiative that uses a naturally occurring bacterium to stimulate the ability mosquitoes to transmit or reduce diseases such as dengue fever.

It's called Wolbachia, and scientists of the program inject it into mosquito eggs to make them dengue-resistant, and then give the eggs or adult mosquitoes to communities where dengue fever predominates.

"There is growing evidence in every country we work that this is a practical and effective way to stop dengue fever," said Peter Ryan, business development director, The World Mosquito Program.

In ongoing field trials in 10 countries around the world, the team found that mosquitoes transmitted Wolbachia bacteria from generation to generation – meaning that these mosquitoes did not transmit dengue.

The program was a success in North Queensland, Australia, where the first trials took place in 2011.

"We have seen an almost complete elimination of dengue fever in areas of northern Queensland where we have now successfully introduced Wolbachia, which is 300,000 people in areas since the 1980s suffered from the scourge of dengue almost every year since the 1980s and we have now experienced a total collapse. "

Experiments in Vietnam and Indonesia also yield positive results.

  Dengue fever: How a mosquito infects millions and not with malaria

"The challenge is how to scale this quickly to make it an affordable intervention," said Ryan. Your goal is to reduce the cost of the program to about 1 USD for each person who helps it, so that in some cases it can be introduced to the world's poorest nations. The end of the field trials is expected in about 18 months.

Progress is also being made on the climate front. Lowe's team is studying how dengue-based countries can set up early warning systems to predict future abnormal climates and prepare for potential outbreaks.

"We can no longer rely on seasonal averages or average conditions to determine when dengue fever reaches its peak" Lowe said.

"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 alter the time intensity of outbreaks."

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

"We encourage countries to focus on better patient management," Abeyasinghe said. "Because if you treat the patient and prevent it from happening, then we're basically making dengue fever a kind of normal flu-like thing that comes and goes."

Sandi Sidhu and Swati Gupta of CNN contributed to this report.


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