C.D.C. Warns Medical doctors About Dengue as Virus Spreads to New Areas

Federal well being officers warned that the danger of contracting dengue in the US has elevated this yr, a worrying signal as world circumstances of the mosquito-borne illness hit document numbers.

Within the first half of this yr, international locations within the Americas reported twice as many circumstances as had been reported in all of 2023, the Facilities for Illness Management and Prevention reported Thursday in an alert to well being care suppliers.

The area has seen practically 10 million circumstances of the virus to this point in 2024, most of which originated in outbreaks in South American international locations like Brazil and Argentina.

Whereas the native transmission of the virus within the mainland United States has been restricted, Puerto Rico, which is assessed as having “frequent or steady” dengue threat, declared a public well being emergency in March and has reported practically 1,500 circumstances.

Instances of dengue fever, a mosquito-borne viral sickness that may be deadly, are surging world wide. The rise is going on each in locations which have lengthy struggled with the illness and in areas the place its unfold was unheard-of till the final yr or two, together with France, Italy and Chad, in Central Africa.

There have even been a couple of hundred circumstances of native transmission in the US. Florida well being officers urged the general public to take precautions — like sporting bug spray and dumping out standing water — after reporting a domestically acquired case of dengue this month.

What’s dengue fever, and why is it changing into extra widespread?

Dengue, a viral fever, is transmitted by Aedes species of mosquitoes. It could trigger excruciating joint ache. Additionally it is recognized by a grim nickname: breakbone fever.

The Aedes aegypti mosquito, which has been driving lots of the present outbreaks, is native to Africa, the place it initially lived in forests and consumed animals. However many years in the past the species unfold to the remainder of the world through commerce routes.

It tailored to city areas, feeding on individuals and breeding in small bits of trapped water in locations equivalent to outdated tires, discarded bottle caps, and trays used to catch air-conditioner drips.

Now, as extra individuals transfer to city areas — many to lower-quality housing in creating international locations — they’re extra weak to the virus. And local weather change is bringing the mosquito to new locations, the place it’s flourishing.

“Aedes mosquitoes thrive in heat and humid environments, so undoubtedly local weather change and rising temperatures and in addition excessive climate occasions are serving to prolong their habitat vary,” mentioned Dr. Gabriela Paz-Bailey, chief of the dengue department on the C.D.C.’s Nationwide Heart for Rising and Zoonotic Infectious Illnesses.

How harmful is dengue?

Just one in 4 dengue circumstances are symptomatic. Some infections might produce solely a light flulike sickness. However others can lead to dreadful signs, together with headache, vomiting, excessive fever and aching joint ache. Full restoration can take weeks.

About 5 p.c of people that get sick will progress to so-called extreme dengue, which causes plasma, the protein-rich fluid part of blood, to leak out of blood vessels. Some sufferers might go into shock, inflicting organ failure.

Extreme dengue has a mortality fee of as much as 5 p.c in individuals whose signs are handled. Left untreated, nonetheless, the mortality fee is 15 p.c.

Extreme dengue might go untreated as a result of sufferers reside removed from medical care or can’t afford it. It could occur as a result of hospitals are overwhelmed with circumstances throughout an outbreak, or as a result of dengue isn’t identified in time because it seems in a brand new space.

Who’s in danger?

Already 40 p.c of individuals globally reside in areas the place they’re prone to dengue an infection; the illness is commonest in tropical international locations, equivalent to Brazil.

The individuals most weak to dengue reside in housing that doesn’t maintain mosquitoes away from them. In research on communities alongside the U.S. southern border, in areas the place the Aedes aegypti mosquito is effectively established, researchers discovered that there have been as many or typically much more of the mosquitoes on the Texas aspect, however far fewer dengue circumstances on the Mexican aspect.

That’s as a result of extra individuals on the U.S. aspect of the border had screened home windows and air-conditioners, which restricted their publicity to mosquitoes, and lived farther aside and had been much less social.

By making fewer visits to associates and kinfolk, residents had been much less more likely to take the virus into new areas the place a mosquito would possibly decide it up from them and move it on.

It’s unlikely that dengue will turn into a significant issue in the US, “so long as individuals conserving residing like they’re residing now,” mentioned Thomas W. Scott, a dengue epidemiologist and professor emeritus at College of California, Davis.

Exterior of Puerto Rico, most dengue circumstances in the US consequence from journey to international locations the place the virus is endemic. However scientists say dengue will proceed to unfold to locations that haven’t skilled it earlier than.

Along with local weather change, rising charges of urbanization world wide are taking part in a task, mentioned Alex Perkins, who’s an affiliate professor of organic sciences on the College of Notre Dame and an professional within the mathematical modeling of dengue transmission.

If individuals have just lately come from rural areas, they’re unlikely to have precedence immunity, so the virus can transfer swiftly via the inhabitants.

“I believe the final expectation that that is going to be a rising drawback in the US is cheap,” he mentioned.

Dr. Perkins mentioned the expertise in southern China provides a cautionary story. Traditionally, the area noticed solely a handful of dengue circumstances annually. Then in 2014, there have been 42,000 circumstances in Guangdong Province.

“Abruptly in a single yr, it grew by a few orders of magnitude with none actual forewarning,” he mentioned.

“In endemic settings, we’re persevering with to have document years, yr in and yr out, and that’s what’s driving all these imported circumstances in the US and elsewhere,” he added.

“And on the subject of the extra marginal transmission settings, such because the southern United States, Southern Europe, China — it’s not getting higher there both. So it’s actually getting higher nowhere: it’s all unhealthy.”

Is there therapy for dengue?

There isn’t a therapy for dengue an infection. Sufferers’ signs are managed with medicines, equivalent to these wanted to regulate ache. However drug firms have antivirals in medical trials.

Is there a vaccine?

The hassle to discover a dengue vaccine has been lengthy and sophisticated.

Dengvaxia, a vaccine developed by the French agency Sanofi, was rolled out extensively in international locations such because the Philippines and Brazil in 2015. However two years later, the corporate mentioned it was inflicting vaccinated individuals who caught the virus to have extra extreme circumstances.

The C.D.C. recommends Dengvaxia just for use in endemic areas for sufferers with a laboratory-confirmed earlier dengue an infection.

The World Well being Group just lately advisable a brand new vaccine, referred to as QDENGA, which can be utilized no matter prior an infection standing, for youngsters aged 6 to 16 residing in areas with excessive dengue transmission.

The vaccine has already been launched in Indonesia, Brazil, Thailand and 16 European international locations, together with Britain and Italy. However it received’t be out there in the US anytime quickly.

What else can we do?

Some international locations have acted aggressively in opposition to dengue and are managing to regulate it. Singapore, for instance, makes use of a mix of strategies, together with the inspection of properties and development websites for breeding areas, with excessive fines for guidelines violations.

“It’s a profitable method, however they’ve a extremely massive finances to assist these actions,” Dr. Paz-Bailey mentioned. “However not each nation has that.”

Brazil and Colombia have had success deploying a micro organism referred to as Wolbachia. When Aedes aegypti mosquitoes are contaminated with the micro organism, they will not move on the dengue virus.

Researchers in South American are mass-producing mosquitoes contaminated with Wolbachia and releasing them to breed with wild bugs in an effort to get the micro organism via the mosquito inhabitants.