2024-04-11 16:41:00
Brazil is currently experiencing the worst dengue outbreak in its history.
The dengue virus is transmitted by mosquitoes. (Symbolic image) – AFP/Archive
It’s tropical and humid and the laboratory in the Brazilian metropolis of Rio de Janeiro is whirring and shaking. Millions of mosquitoes are bred here to help combat one of the biggest health problems of the South American country today. Brazil is currently experiencing the worst dengue outbreak in its history.
Since the beginning of the year, almost three million probable infections with the dengue virus have been registered in the South American country, the Ministry of Health announced on Wednesday. Brazil has long since broken the historic record of 2015, when around 1.6 million dengue cases were registered throughout the year.
Public health emergency in ten states
So far, 1,117 deaths due to dengue infection have been confirmed – that is also a sad record. That is more deaths since the beginning of the year than in all of 2023, when there were 1,094 deaths.
A total of 1,806 additional suspected cases are still being investigated. However, the number of unreported cases is likely to be many times higher. Ten states and the capital district have now declared a public health emergency.
Modified mosquitoes
There are various options to combat the massive spread of dengue fever. One strategy: modified mosquitoes. The World Mosquito Program (WMP) has developed a method to neutralize viruses in mosquitoes using Wolbachia bacteria, which occur naturally in many insect species.
Researchers have found that this bacterium prevents the growth of viruses such as dengue in yellow fever mosquitoes (Aedes aegypti) – which transmit these viruses, among other things – and reduces their occurrence in the population.
“The entire environment necessary for the mosquito is recreated in the biofactory,” says a WMP spokesman. The temperature is between 28 and 30 degrees and the environment is humid.
About ten million mosquito eggs containing Wolbachia bacteria are produced every week, and the mosquitoes are then released into areas where dengue viruses are widespread. Through reproduction, they spread the Wolbachia bacteria over several generations.
The first successes are already there
In Niterói, the sister city of Rio de Janeiro on the opposite side of Guanabara Bay, the spread of dengue has already been significantly reduced using this method. Mosquitoes carrying Wolbachia bacteria have been released there since 2015. As a result, the number of dengue infections has fallen by 70 percent, said the research institute Fiocruz according to a 2021 study.
In Rio, these mosquitoes are also bred in the laboratory, but so far they have only been released in some neighborhoods – unlike in Niterói, where, according to the WMP spokesman, they are released throughout the area. According to the Ministry of Health, the incidence, measured in cases per 100,000 inhabitants, is around seven times higher in Rio than in Niterói.
Dengue fever is known as bone-breaking disease
Dengue fever – sometimes called bone crusher’s disease because of the pain – is widespread in the tropics and subtropics. The course of the disease is often mild and not everyone who is infected becomes ill.
The heavy rains and high temperatures of the past few months are likely to have triggered the sharp increase. The yellow fever mosquito can develop particularly well under these conditions.
In addition to climate, hygiene problems are the main cause
But according to scientists, the climate is not the only reason for the increase. Brazilian cities are growing, and the sanitary infrastructure often cannot keep up, according to a recently published article in the specialist journal “Nature”. Uncollected garbage becomes a breeding ground for insects, as does stored water from people who do not have regular access to tap water.
According to the Nature report, limited natural immunity also contributes to the increase. Dengue fever is caused by four different subtypes of viruses.
After several years in which the first two subtypes predominated in Brazil, the other two have recently returned. Many Brazilians are susceptible to these subtypes and therefore have a higher risk of becoming ill.
Brazil launched a vaccination campaign
In February, Brazil started a vaccination campaign with a new vaccine, initially primarily for children and young people. According to the Ministry of Health, a total of 3.2 million people are expected to be vaccinated with the two doses this year.
According to critics, this is not enough in the country with more than 200 million inhabitants. “To have an impact on the rates, we would need mass vaccination,” says Ana Lúcia de Oliveira, an infectious disease expert at the Federal University in Campo Grande in the state of Mato Grosso do Sul, according to the “Nature” report.
And even widespread vaccination cannot defeat the disease if basic hygiene problems are not addressed, researchers say.
Worst dengue outbreak in the continent’s history
Not only Brazil – the spread of dengue fever has also reached other countries on the continent: More than 3.5 million cases were reported across the American continent in the first three months, as the Pan American Health Organization (PAHO) announced at the end of March.
“This is worrying because it is three times as many cases as in the same period in 2023 – a record year with more than 4.5 million cases reported in the region,” said PAHO director Jarbas Barbosa. The PAHO spoke of what was probably the worst dengue outbreak in the history of the continent.
In addition to Brazil, Paraguay and Argentina are the most affected. With more than 215,000 confirmed infections, Argentina has recorded the worst dengue epidemic in the past 15 years.
Many hospitals in the greater Buenos Aires area are overloaded, and around 90 percent of patients go to the on-call service because they suspect dengue, as the newspaper La Nación reported. In Peru, a state of emergency has been declared for most of the country.
WHO warns Europe
The World Health Organization (WHO) is now warning of an increase in dengue infections in Europe. Although the tropical disease is not endemic in Europe and most cases are imported due to travel, the risk of tiger and yellow fever mosquitoes spreading is increasing as temperatures rise.
It is said that if it gets warmer, eggs can survive the winter and larvae can hatch. In 2023, Italy, France and Spain reported locally transmitted dengue infections.
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