CDC advises US doctors to be cautious about dengue fever as cases rise worldwide

On Tuesday, U.S. health officials urged doctors to be on the lookout for cases of dengue fever as the tropical disease hits new records around the world.

The mosquito-borne virus is spreading worldwide, aided by climate change. In just six months, countries in the Americas have already broken annual records for dengue cases.

The World Health Organization declared a state of emergency in December and Puerto Rico declared a public health emergency in March.

Dengue remains less common in the continental United States, but there have been three times more cases in the 50 states so far this year than at the same time last year. Most infections have been transmitted by travelers abroad, and authorities caution that there is no evidence of a current outbreak.

However, they also warn that local mosquitoes pose a danger.

Last week, a person with locally transmitted dengue fever was reported in Hillsborough County, the eighth locally transmitted case in Florida this year.

According to the Hillsborough Health Department, as of May 18, there have been 173 cases in Florida this year in people who have traveled abroad to a dengue-endemic area.

In a health alert on Tuesday, the U.S. Centers for Disease Control and Prevention (CDC) advised doctors to monitor symptoms, ask questions about patients’ recent travel destinations and order dengue testing if necessary.

Dengue fever is transmitted to humans through the bite of infected female mosquitoes. Aedes Genus, especially Aedes aegypti. According to experts, this warm-weather mosquito is expanding its range due to climate change.

Many infected people do not become ill, but some suffer from headaches, fever and flu-like symptoms. In severe cases, severe bleeding, shock and death can occur.

Repeated infections can be particularly dangerous.

There are four types of the dengue virus, known simply as 1, 2, 3 and 4. When someone is infected for the first time, their body makes antibodies against that type for life. If they become infected with a different type of dengue, the antibodies from the first infection may not be able to neutralize the second type – and may actually help the virus enter immune cells and multiply.

This is a cause for concern in Puerto Rico, where the type 1 virus has been present on a large scale for the past two decades. Last month, the island reported its first dengue death of the year.

“We are currently seeing an increase in cases of dengue 2 and dengue 3, for which the population has very little immunity,” said Dr. Gabriela Paz-Bailey, the Puerto Rico-based chief of the CDC’s dengue division.

There is no widely available medication to treat dengue infections.

Vaccines are a tricky business. US authorities recommended a vaccine from Sanofi Pasteur in 2021. The three-dose vaccine is designed to protect against all four types of dengue and is only recommended for children ages 9 to 16 who have a laboratory history of previous dengue infection and who live in a dengue-endemic area such as Puerto Rico.

Because of these limitations and other problems, the vaccine has not been widely used. As of late last month, only about 140 children in Puerto Rico had been vaccinated since the shot became available there in 2022, and Sanofi Pasteur has notified the CDC that it will stop producing the vaccine.

Another vaccine from Tokyo-based pharmaceutical company Takeda is not currently approved in the United States. Others are in development.

More than 6.6 million infections were reported by around 80 countries worldwide last year. In the first four months of this year, 7.9 million cases and 4,000 deaths were reported, according to the World Health Organization. The disease was particularly severe in the Americas, including Brazil and Peru.

In the US, the numbers were far lower – there were about 3,000 cases in US states and territories last year. However, it was the worst in a decade and included more infections caused locally by native mosquitoes. Most of the cases were in Puerto Rico, but about 180 cases were in three US states – Florida, Texas and California.

There have been nearly 1,500 locally transmitted cases in the United States so far this year, almost all of them in Puerto Rico.

Most cases in the mainland United States continue to affect people who became infected while traveling abroad.

It is “a traveler’s nightmare” and is a growing cause for concern internationally, says Dr. Lulu Bravo, who researches pediatric tropical diseases at the University of the Philippines Manila and has worked with Takeda on its vaccine.

“If there is an outbreak in a country, tourists may not want to come anymore,” Bravo said.

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