Dengue Fever On The Rise

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Tropical diseases are on the rise in the United States and worldwide, including the mosquito-borne “dengue fever.” The Centers for Disease Control and Prevention (CDC) advised healthcare providers nationwide to be on the lookout for symptomatic cases. Although many Americans have a history of having recently traveled abroad, dengue is now thought to also be spreading locally.

At least 2,241 cases have been reported in the U.S. this year, three times more cases than at the same point last year. The greatest number on the mainland have occurred in Florida, Puerto Rico, a U.S. territory, has seen nearly 1,500 individuals afflicted with the infection. Cases also exist in the U.S. Virgin Islands and American Samoa.

Worldwide, dengue is a much worse issue. It affects about 400 million people yearly. In 2019, places as far apart from each other as Singapore, Nicaragua, and Bangladesh reported community-wide outbreaks: not since the beginning of that year, but on the same day.


The virus is spread by infected Aedes Aegyptus, Aedes Albopictus, and other mosquito species acting as “vectors.” Vectors transmit the disease from human to human through their bite, sickening their victims while suffering no ill effects themselves.

(Aside: Only female mosquitoes bite.)

When an infected mosquito bites a person, the virus enters the skin through its saliva. Dengue infects nearby cells in the skin and, then, makes its way to white blood cells, where it reproduces.

There are several different subtypes (called DENV-1, DENV-2, DENV-3, and DENV-4) which present with similar symptoms. Infection with one subtype of dengue usually gives lifelong immunity to that type, but only short-term immunity to the others. If you get infected again with a different subtype, the second infection increases the risk of a more severe version of the disease.



Rates of Dengue infection are also thought to have increased greatly since 1960 due to encroaching civilization and population growth in warmer regions. As a resident of South Florida, I believe that the widespread introduction of residential air conditioning around that time may have precipitated the explosion in potential victims.

Climate change has been blamed for dengue’s spread. Increasingly warm and wet summers are a result of the current El Nino event. The influx of immigrants with asymptomatic dengue may also play a part in local mosquitoes becoming infected in the U.S..


Thankfully, most dengue infections are asymptomatic. If you’re in the unlucky minority that gets sick, you can expect to see signs about four to fourteen days after the infectious bite. You may experience:

  • A high fever (up to 104 degrees Fahrenheit) of sudden onset
  • Severe joint, bone, and muscle pain
  • Severe headaches
  • Pain behind the eyes
  • Fatigue
  • Nausea and vomiting
  • Skin rashes (several days into the sickness)

Sometimes, the orthopedic symptoms are so painful that Dengue has been called “Breakbone Fever”. Thankfully, most resolve their symptoms within a week or two and become immune to the virus (at least the specific strain they contracted; remember, there are four). If someone with a history of Dengue fever gets sick again, it is likely with a different strain.

I mentioned that second dengue infections tend to be worse than the first. Although most will still recover, a small minority will develop a life-threatening version of the disease called “dengue hemorrhagic fever”. The victim may experience resistant fevers, bleeding from nose and gums, blood and lymphatic vessel damage, and liver enlargement. In the most severe cases, the disease may progress further to “Dengue Shock Syndrome” where massive bleeding, organ failure, and circulatory collapse occurs. If you had to compare it to another disease, think of end-stage Ebola or Marburg.


There is no specific therapy that cures dengue fever. Treatment is symptomatic; for example, acetaminophen for fever. NSAIDs like ibuprofen should be avoided due to bleeding risks. Ensuring the patient is well-hydrated is extremely important, as is bedrest.

There are dengue vaccines that are given in special cases, such as if this is a second infection, or the patient lives in an area where dengue is common. Vaccines are also recommended by the CDC for U.S. territories.


mosquito netting

In the U.S., the majority of the cases occur in travelers who went to areas where dengue is well-established. But, because mosquitoes are so widespread, local spread of dengue is highly likely. No matter the location, the best way to prevent catching the disease is to avoid mosquito bites.

If you live in an area where there is a large mosquito population, you can best protect yourself with a few precautions:

  • Use DEET or other mosquito repellant regularly (even indoors in some areas).
  • When outdoors, wear long-sleeved shirts.
  • When outdoors, wear long pants and tuck the cuffs into your socks.
  • Clothing can be sprayed with the insecticide Permethrin 0.5% (but not skin).
  • If you have air conditioning, keep the windows and doors shut.
  • If you don’t have air conditioning, use mosquito netting and door/window screens.
  • Reduce the mosquito population by eliminating standing water wherever possible. Eliminate junk like tin cans, flowerpots, and old tires that could serve as breeding grounds. Bird baths and your pet’s water dish may also support mosquito larvae.
Mosquito Larvae In Garbage Can Water

People should be especially cautious about prevention if they are planning to travel to Latin America, which has seen a record-breaking number of cases.

In olden days, epidemics of tropical disease killed residents of southern cities in the U.S., such as New Orleans. These can become serious issues again in disaster settings. Be sure to acquire knowledge about the recognition and treatment of the infectious diseases that can affect your region. If you do, you’ll be more likely to succeed, even if everything else fails.

Joe Alton MD

Dr. Joe Alton

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