Whether you are gardening, enjoying a barbecue or gathering with friends to watch July 4th fireworks, mosquitoes can be one of the most irritating things about being outside during the warm summer months. But mosquitoes aren’t just itchy and annoying. They can also spread diseases.
Three mosquito-born diseases have been reported in Georgia this year but only one is the subject of global alerts this summer. Health officials are watching for dengue fever, which is soaring in more tropical climates. While 14 cases of dengue has been seen in Georgia, all of the cases were related to travel outside the U.S., according to the Georgia Department of Public Health. The 20 cases of malaria and the single case of chikungunya reported this year are also related to international travel.
Last week, the Centers for Disease Control and Prevention warned about an increased risk for dengue fever infections in the U.S. as global cases of this mosquito-borne disease hit record numbers. This week a dengue fever alert was issued in the Florida Keys following two locally acquired cases of the mosquito-borne illness there.
The CDC is urging clinicians to stay on alert for symptoms and ask patients about any recent travel as cases are surging around the globe.
Experts say Georgia residents should take precautions against mosquito bites, but they stress it’s unlikely for dengue to begin spreading here. Georgians are far more likely to be infected by West Nile virus, which has caused 81 infections in the state from 2018 to 2022.
Dengue is the most common mosquito-borne infection worldwide, but in the U.S., most dengue cases are associated with travel to tropical and subtropical locations, such as the Virgin Islands, Puerto Rico and South America. So far this year, there have been nearly 1,500 locally acquired U.S. cases of dengue, nearly all of them in Puerto Rico.
Mosquito-borne diseases are spread to humans through the bites of infected mosquitoes. They do not spread from person to person.
Dengue fever is mainly spread by the bite of infected Aedes aegypti mosquito or yellow fever mosquito, a type of mosquito that is very rare in Georgia. But the Aedes albopictus or Asian Tiger mosquito — which is very common in Georgia — has shown it can also transmit dengue in other places outside Georgia.
Experts say Georgians face a greater risk for dengue when they travel.
Gonzalo Vazquez-Prokopec, an expert in vector ecology and control at Emory’s Department of Environmental Sciences, said the growth in dengue cases is fueled by high temperatures brought by last year’s El Niño — a climate pattern marked by warmer-than-average ocean temperatures.
A post-pandemic travel boom is also playing a role in the uptick. “Human mobility, either short or longer distances, plays a significant role in moving viruses around,” he said.
If a mosquito bites someone infected with dengue, it can spread the virus to other people. That means local outbreaks become possible when people import the virus.
But with the number of Georgia travelers infected with dengue so small, the potential for this disease to spread locally in Georgia remains very low, especially because the type of mosquito (Aedes aegypti) that spreads dengue is rare in Georgia.
Credit: Steve Nowland
Credit: Steve Nowland
There is no specific medicine to treat dengue, and there are no vaccines for adults or people without a previous dengue infection.
Only one out of four dengue cases have symptoms. While some infections produce only mild symptoms, others can produce headaches, high fever, aching joint pain and can take weeks for recovery. About 5% of people infected with dengue will have severe dengue which can lead to shock, internal bleeding, organ failure and even death.
Vazquez-Prokopec said precautions to avoid mosquito bites should be taken for those traveling to places where dengue is spreading, and travelers should also take steps to prevent being bitten upon returning home. Many people infected dengue don’t experience symptoms and won’t even know they have it.
Elmer Gray, an entomologist with University of Georgia Cooperative Extension Service, said features taken for granted in higher-income countries help lower and prevent exposure to disease carrying mosquitoes and can help prevent continuous spread. Air conditioning, screens on windows, and drainage systems all reduce mosquito breeding and exposure.
Malaria was once a prevalent disease in the U.S. but was eradicated in the early 1950s through the use of insecticides, drainage ditches, and window screens. The last locally acquired malaria case in Georgia goes back at least two decades to a probable case in 1999, according to the DPH. In Florida, there were seven cases of locally acquired malaria last year.
Gray, who is a public health extension specialist and whose research mainly focuses on mosquitoes and other insects such as black flies, said the West Nile virus, a virus spread locally by mosquitoes in Georgia, continues to pose a threat to Georgians. He said there were 19 cases of West Nile virus in Georgia last year and two of those died from complications from the virus. There been no reported human cases yet this year, but it’s still early with the season typically peaking in August and September.
West Nile is most often carried in Georgia by the Southern house mosquito which is very common throughout the state. In most cases a healthy immune system can fight off West Nile. But in rare cases — typically involving elderly people, those with compromised immune systems or very young children — the disease can progress and show symptoms such as a fever and rash. In extremely rare cases, the virus can lead to encephalitis (swelling of the brain) and death.
Eastern Equine Encephalitis (EEE) is another mosquito-born disease that has shown up in Georgia. It is extremely rare with four cases in the state between the years of 2018 and 2002. Mosquito species known to carry EEE are found mostly in coastal, swampy areas of the state.
Georgia is home to 63 mosquito species. And when it comes to battling mosquitoes of all kinds, vigilance is the key, according to experts.
Just how bad mosquitoes will get in metro Atlanta this summer remains to be seen. Mosquitoes like it hot, but they also need standing water in order to complete their life cycle. This dry stretch of scorching hot temperatures means a decrease in the overall mosquito populations, especially those that prefer hot and wet conditions.
But weather conditions can quickly change.
“So here we are in July with people going out at dusk, which is when most of the mosquitoes are active,” said Gray. “If we do have bad mosquitoes in metro Atlanta, it’s because something is being missed. There’s a container, an abandoned pool, there’s a tire (with standing water). Take a few precautions. Light-colored loose fitting clothes, EPA-approved repellents. A few precautions can go a long way.”
Tips to avoid mosquito bites:
1. Wearing light-colored clothing. Mosquitoes are more attracted to people wearing darker colors because they stand out more.
2. When outside in a mosquito-prone area, insect repellent is the most effective step. There are several commercially available, EPA-approved repellents, like picaridin, lemon eucalyptus oil and IR3535. Gray prefers products with DEET because they have been tested and proved safe for children as young as 2 months old. When treating children, an adult should apply the repellent to his or her hands first and then rub the repellent onto the child’s exposed skin, but never on a child’s hands because small children have a habit of sticking their hands in their mouths.
3. Mosquitoes need standing water to reproduce, so eliminate sources of standing water in yards and landscapes.
4. Keeping grass trimmed and the vegetation around the borders of the yards cut back to reduce the areas where adult mosquitoes hide during the heat of the day.
5. Mosquitoes are most active at dawn and dusk, so stay inside during those times to avoid bites.
6. If sitting on your porch or deck, a box fan can deter mosquitoes.
Source: Elmer Gray, entomologist with University of Georgia Cooperative Extension Service
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