Brazil is experiencing a dengue emergency, heralding a health crisis in the Americas
Brazil is experiencing a massive outbreak of dengue fever, a sometimes fatal disease transmitted by mosquitoes, that public health experts say is a harbinger of a coming surge in cases in the Americas, including Puerto Rico.
The Brazilian Ministry of Health warns that it expects more than 4.2 million cases this year, which exceeds the 4.1 million cases recorded by the Pan American Health Organization in all 42 countries of the region last year.
Brazil was set to have a bad year for dengue fever – virus case numbers typically rise and fall over the course of about four years – but experts say a number of factors, including El Niño and climate change, have dramatically worsened the problem this year.
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“The country’s record temperatures and above-average rainfall since last year, even before summer, have led to an increase in the number of mosquito breeding sites in Brazil, even in areas that have seen few cases of the disease,” Brazilian Health Minister Nicia Trindade said. He said.
Dengue case numbers have already risen in Argentina, Uruguay and Paraguay in the past few months, during the Southern Hemisphere summer, and the virus will move across continents with the seasons.
“When we see waves in one country, we will generally see waves in other countries; “That’s how interconnected we are,” said Dr. Albert Ko, a dengue expert in Brazil and a professor of public health at Yale University.
The World Health Organization has warned that dengue fever is fast becoming a pressing global health problem, with a record number of cases recorded last year and outbreaks in places, such as France, that have historically not reported the disease.
In the United States, Dr. Gabriela Paz Bailey, chief of the dengue branch of the Division of Vector-Borne Diseases at the Centers for Disease Control and Prevention, said she expects dengue infection rates to rise in Puerto Rico this year and that there will be more cases in the continental United States as well. Especially in Florida, but also in Texas, Arizona and Southern California.
Dengue is spread by Aedes aegypti, a type of mosquito that has begun to settle in new areas, including warmer, more humid parts of the United States, where it had only been seen in the past few years.
Cases in the United States are still expected to be relatively few this year — in the hundreds, not millions — because of the prevalence of air conditioners and window screens. But Buzz Bailey warned: “When you look at the trends in case numbers in the Americas, it’s scary. It’s been constantly increasing.”
Florida reported the highest number of locally acquired cases last year, 168, and California reported its first such cases.
Three-quarters of people infected with dengue fever have no symptoms at all, and among those who do, most cases resemble only mild flu. But some dengue infections are serious, causing headaches, vomiting, high fever and joint pain that gives the disease the nickname “break-bone fever.” A bad case of dengue can leave a person exhausted for weeks.
About 5% of people who contract the disease will develop what is called severe dengue fever, which causes plasma, the protein-rich fluid component of blood, to leak from the blood vessels. Some patients may go into shock, causing organ failure.
The death rate in severe dengue cases is 2% to 5% in people whose symptoms are treated with intravenous blood and fluid transfusions. However, if left untreated, the mortality rate is up to 15%.
In Brazil, state governments are establishing emergency centers to test and treat people with dengue fever. The city of Rio de Janeiro declared a public health emergency over dengue fever on Monday, days before the start of the annual Carnival celebration, which brings together tens of thousands of people for outdoor parties during the day and nights.
Trindade said large numbers of cases have been reported in Brazil’s southernmost states, which are typically much colder than Rio and states in the center and north. People in those areas will have little immunity to the disease from prior exposure.
Dengue comes in four serotypes, similar to their viral cousins. Previous infection with one of these viruses provides only short-term protection against infection with another, and a person who has been infected with one dengue serotype in the past is more likely to develop severe dengue than is infected with another serotype.
“Right now, there are serotypes circulating in Brazil that haven’t been circulating for 20 years,” said Dr. Ernesto Marques, associate professor of infectious diseases and microbiology at the University of Pittsburgh.
Brazil has begun an emergency campaign to vaccinate children in areas with the highest rates of dengue transmission or risk of transmission, using a two-dose vaccine called Qdenga made by Japanese pharmaceutical company Takeda. Brazil has purchased 5.2 million doses for delivery this year, plus another 9 million doses for delivery in 2025, and the company has donated an additional 1.3 million doses, effectively securing most of Qdenga’s supply globally. A company spokesman said Takeda is working on a plan to increase supply, with a focus on delivery to countries with high infection rates.
But even then, this is enough to cover less than 10% of Brazil’s population over two years. The only good news about dengue in Brazil at the moment is the publication of the results of clinical trials of a new vaccine tested by the public health research center Butantan Institute in São Paulo. This vaccine requires only one injection, and the trial found that it protects 80% of those vaccinated against dengue virus infection. The research center will ask the Brazilian government to approve the vaccine, and it has facilities to produce it, with the aim of starting to deliver doses in 2025.
For this outbreak, it’s too late for vaccination to help much, and there are few other ways public health authorities can slow it down.
“Insecticide resistance really limits what you can do in terms of controlling mosquito populations, and insecticide resistance is widespread,” Buzz Bailey said. “What you can do is make sure that people have access to clinical management and that doctors know what to do.”
Medical centers in Brazil are preparing extra beds for people with severe dengue fever, hoping to prevent the kind of health system overwhelm that occurred during the COVID-19 pandemic and prevent dengue deaths.
“The old model of dengue affecting children more is not the case in Brazil – you have to think about the elderly, who are very vulnerable,” Ko said. He said it would be important for both doctors and the public to receive the message to get tested for dengue at the first sign of symptoms in both children and the elderly.
“Any safe guess was that this year would be bad, but now we know how bad it will be,” Marquez said. “It will be very bad.”
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