Latest Infectious Disease News
Florida, in the throes of a COVID-19 surge, has mobilized air assets, trucks and foot soldiers in a battle on another public health front: The mosquito-borne dengue fever has infected more than a dozen residents over the last few weeks.
People in Key Largo have probably noticed the Florida Keys Mosquito Control District helicopter that commandeered the vacant local high school stadium Monday. The pilot leaves the makeshift base to douse the surrounding countryside with mosquito larvicide twice a week, according to a district press release.
The pesticide in use is a concentrated solution containing a common soil bacteria, Bacillis thuringiensis, which is deadly to mosquito larvae and harmless to humans and vertebrate animals.
Accompanying the mosquito attack chopper and larvicide spray trucks are workers going door-to-door to make sure residents keep standing water off their property, the district states in a press release.
Even a few ounces of rainwater in an old tire or collected on a boat tarp can breed thousands of the Aedes aegypti mosquitoes that carry dengue fever, Zika, West Nile and other nasty viruses once confined to tropical regions, according MedicineNet author Sandra Gonzalez Gompf; MD, FACP.
In addition to spraying and inspecting, Florida mosquito control officials will be setting traps throughout the region to capture and test mosquitoes for presence of the virus.
The number of infections is low – only 14 centered on Key Largo as of July 11, according to the Miami Herald. What worries health officials about this outbreak is they believe each infection was community-acquired. This means the people caught the virus from a mosquito bite in Key Largo, not on a trip to, say, Indonesia or some other tropical destination where the disease is endemic.
Dengue fever is marked by flu-like symptoms that last a couple weeks. Common strains of dengue are fatal less than 1% of the time, but the rarer and more serious dengue hemorrhagic fever that affects children is much more serious. This is a complication of severe dengue, but Florida officials have not reported any cases of DHF.
What Is Dengue Fever?
Dengue fever is an acute illness of sudden onset that usually follows a benign course with symptoms such as:
- severe muscle and joint pain,
- swollen lymph nodes (lymphadenopathy), and
A virus causes dengue fever, and there is no specific medicine or antibiotic to treat it. For typical dengue fever, the treatment is directed toward relief of the symptoms. Papaya leaf extract may offer some symptom relief, Dr. Cunha said.
The virus is not contagious person-to-person. You can only get it via mosquito bite, Dr. Cunha said.
How Do You Prevent Dengue Fever?
Avoiding mosquitoes is important to avoid contracting dengue fever. In dengue-endemic tropical and sub-tropical areas, you should wear light-colored long-sleeved shirts and long pants or trousers, use insect repellent, stay or sleep indoors in air conditioning when possible and use mosquito netting over the bed if available, Cunha said.
Aside from time-tested mosquito control methods like larvicide and eliminating standing water, researchers are testing campaigns to wipe out enough of the mosquito population in a given disease outbreak area using genetically modified male mosquitoes who produce offspring with fatal birth defects, according to USA Today.
England’s Oxitec Ltd. got approval from the U.S. Environmental Protection Agency May 1 to release their patented “friendly” mosquitoes at Florida locations with endemic dengue, but Friends of the Earth and other environmental groups are fighting the project in court. They killed the first iteration of Oxitec’s mosquito plan in 2016, according to USA Today.
Though experimental efforts by the biotech firm have met with some success in Brazil, some environmental activists and researchers worry the GM mosquitoes could accidentally produce viable offspring through mutation, making the local population of mosquitoes genetically more robust in the long term.
Scientists disagree on this potential, however, according to discussions on the project published in Scientific Reports.
The U.S. FDA approved Dengvaxia, a vaccine for dengue fever, in May 2019 for use in dengue-endemic areas. Currently, because there are so few cases in the U.S., the vaccine is approved only for those who are especially vulnerable and also live in dengue-endemic areas like south Florida, Puerto Rico, Guam or the U.S. Virgin Islands, Dr. Cunha said.
How to Keep Mosquitoes from Breeding on Your Property
You can do a great deal to control disease-carrying mosquitoes simply by inspecting areas around the house where even a bottle cap full of water may collect, and emptying them, Dr. Gompf writes. For example:
- Pots should be stored upside down to prevent water collection or stored inside.
- Rain gutters should be inspected and cleared of debris that can block drainage.
- Used tires should be disposed of by recycling or at tire disposal centers. Stored outdoors, they make excellent mosquito incubators, offering pockets of stagnant water and shelter from the elements.
- Stay indoors at dawn, dusk, and in the early evening.
- Wear long-sleeved shirts and long pants when outdoors.
- Take preventive measures in and around your home. Repair or install door and window screens, use air conditioning, and reduce breeding sites (eliminate standing water).
- Note: Vitamin B and "ultrasonic" devices are not effective in preventing mosquito bites.
How to Prevent Mosquito Bites
Dr. Gompf offers the following instructions for picking clothing and applying insect repellent to maximize your chances of avoiding mosquito bites that could carry disease:
- Apply EPA-registered insect repellent sparingly to exposed skin and clothing according to manufacturer's instructions. An effective repellent contains 20%-30% DEET (N,N-diethyl-meta-toluamide). DEET in high concentrations (greater than 30%) may cause side effects, particularly in children and babies, but it is safe to use in pregnancy. Avoid products containing more than 30% DEET.
- Picaridin is a newer repellent that is effective and about as long-lasting against mosquitoes as DEET at the same concentrations. It has been used in Europe and has been available in the U.S. since 2005. Unlike DEET, picaridin has no odor, does not damage synthetic fabrics and plastics, and is non-greasy.
- There are some repellents with essential oils like geranium oil that may be an option for some people, but there is much less data on duration of protection or reliability of protections against mosquitoes.
- B vitamins are not effective repellents against mosquitoes.
- Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children. Insect repellents should not be applied to very young children (under 3 years of age) or babies.
- Spray clothing with repellents containing picaridin or DEET since mosquitoes may bite through thin clothing. There are permethrin products that can be applied to clothing that will remain effective through a few washes. For those who work outdoors or need extended protection, permethrin-impregnated clothing is also available.
- Whenever using an insecticide or insect repellent, be sure to read and follow the manufacturer's directions for use, as printed on the product.