Where Are Mosquitoes Most Likely to Carry Dengue, According to the CDC?
On Tuesday, the CDC issued a public health advisory warning health care workers and the general public that there is an increased risk of contracting dengue infections in the United States. Dengue is a mosquito-borne disease that can be quite brutal (severe cases are sometimes called “break-bone fever”), but some of us can relax a little: The mosquitoes that transmit it only live in certain parts of the United States.
What is dengue?
Dengue is a viral disease and the virus is transmitted by mosquitoes, especially Aedes species. (Yes, there are different types of mosquitoes.) They are mainly found in tropical and subtropical regions.
There are four types of dengue fever, numbered simply 1, 2, 3 and 4. If you get one and recover, you will be immune to that type but will remain susceptible to the others. Re-infection with a different type of dengue than the first increases the risk that your illness will be more severe.
Symptoms of mild dengue fever include high fever, body aches and often a rash. You may also experience nausea and vomiting, as well as a headache and/or pain behind the eyes. According to the World Health Organization, most people recover within 1 to 2 weeks.
In severe cases of dengue fever, additional symptoms may appear after the fever subsides. These include severe abdominal pain, bleeding from the gums or nose, blood in the vomit or stool, and feeling extremely tired, thirsty and weak, according to the WHO. Dengue is the most common insect-borne disease in the world.
There is no antiviral treatment for dengue fever, only supportive care. There was a vaccine available for children in areas where dengue fever is endemic, but the manufacturer discontinued it due to lack of demand, the Centers for Disease Control and Prevention (CDC) said in its health advisory. Puerto Rico declared a dengue epidemic earlier this year and they are using the remaining available doses before they expire.
Most cases of dengue in the continental US come from travelers, but we do have some cases of local transmission.
With CDC recommendations making headlines, it’s important to remember where dengue is currently being transmitted. In most of the continental United States, local transmission of dengue is not observed; you can’t go outside and catch it right now.
So why the recommendation? Well, many of the places where you can get dengue are popular holiday destinations. According to the CDC, there are also several US territories and freely associated states that experience “frequent or persistent” transmission of dengue:
-
Puerto Rico
-
American Samoa
-
US Virgin Islands
-
Federated States of Micronesia
-
Marshall Islands
-
Palau
Dengue can be contracted locally in the continental United States, but cases are few and far between. Local transmission of dengue has been reported in Florida, Hawaii, Texas, Arizona and California.
This year, there have been 1,498 cases reported in Puerto Rico and 745 cases associated with travel to the United States (meaning someone traveled to an area with dengue and then brought the virus with them). A travel case may develop into a local outbreak, although this is uncommon. Let’s say your neighbor just returned from vacation to Puerto Rico and you both live in Florida. The mosquito may bite that person and then bite you. Therefore, the CDC asks health care providers to remember that a person who has not traveled can still become infected with dengue locally if they live in an area where suitable mosquito species are found.
Where do mosquitoes that carry dengue live?
Dengue is transmitted by mosquitoes of the genus Aedes , especially Aedes aegypti , but sometimes Aedes albopictus . These mosquitoes are small, have black and white patterns (if you look closely), and they bite during the day, not just at dusk and dawn. They can also breed in very small containers of standing water, such as saucers under flower pots.
These differences distinguish them from Culex mosquitoes, which are the more common type throughout much of the United States. Culex mosquitoes are not considered “competent” vectors of dengue fever, so if your area only has Culex , you’ll only have to worry about travel and not travel. (probably) local.
So where are the Aedes mosquitoes? The most recent CDC maps are from 2017, but here they are. A. aegypti is “very likely” to thrive across much of the South, from Florida to Texas and down to Kentucky and parts of Oklahoma and Missouri. There are also “very likely” areas in Texas, Arizona and California.
Aedes albopictus can live and breed in many of the same places, but are less likely to thrive in Arizona and California. On the other hand, the northernmost part of their range extends a little further, all the way to Ohio, New Jersey and parts of Pennsylvania.
In the seven years since these maps were published, the mosquito’s range may have expanded. Aedes mosquitoes love warm temperatures, and climate change has given us even more of them. Dengue is also more easily transmitted during warmer and wetter periods of the year, and we are seeing more cases of this as well.
How can I protect myself from dengue?
The CDC recommends that we all take steps to protect ourselves from mosquito bites. This includes using EPA-registered repellents on your skin. I like Cutter Skinsations (7% DEET, enough for my yard), but there is also Repel 100 if you want very strong protection.
Air conditioning, window screens and loose, long-sleeved clothing are also among the CDC’s top tips for preventing mosquito bites. If you’re traveling to a warm or tropical country, the CDC wants you to also take care to prevent bites while you’re there. Large bottles of insect repellent, since it’s liquid, will have to be carried in checked luggage, but I love these prepackaged repellent wipes that you can take in your carry-on luggage.
The CDC also wants you to seek medical attention if you develop symptoms that may be related to dengue and if you are in an area where dengue transmission is known to occur. The incubation period is seven to ten days, so it is possible that symptoms will not begin to appear until after you return home. The Centers for Disease Control and Prevention (CDC) has a list and map of places outside the United States where the risk of dengue fever is high.