The territory is taking a multipronged approach, including the use of larvicides, in response to a growing chikungunya epidemic, but Health Department officials said at a press conference Tuesday they will not be fogging the streets because the data shows it will not help.
"There has been a lot of testing and fogging just isn’t an effective approach," said Brett Ellis, a Health Department entomologist or insect scientist. "I’m not saying fogging just doesn’t work at all. It just doesn’t work against this mosquito," he said.
The problem is that Aedes aegypti, the mosquito that spreads chikungunya and also dengue, spends a lot of its time indoors near people, in dark places like closets or under beds, and does not come into contact with the chemicals when sprayed, Ellis said. And since in the U.S. Virgin Islands many rely on rainwater collected in cisterns, the quality of that water could be affected by fogging, he said.
Health Commissioner Darice Plaskett read a statement saying the chemical used by the territory for fogging in the past, permanone 30-30, is very unstable in water and the Environmental Protection Agency has raised concerns regarding the contamination of rainwater sources such as cisterns and wells.
The EPA has imposed buffer zone of 25 to 50 feet and requires monitoring of rainwater sources in areas where fogging is conducted to assess for contamination. Studies have also shown it has not worked to stop the spread of the chikungunya virus, she said.
Health Department epidemiologist Dr. Esther Ellis said the number of cases is continuing to increase, with most cases on St. Thomas, but some on every island, adding that as mosquito eradication efforts bear fruit, the numbers should begin to drop off. However, she said, "as long as we have continual rain like this, there is going to be a source" of mosquitos.
The fact that chikungunya is new to the region helps explain both why it is spreading fast and why most cases are on St. Thomas. Ellis said it frequently takes multiple cases for a virus to become established, because mosquitos have to bite an infected person and then bite another person. On St. Thomas, "it was probably multiple infected people in a section of the island" who then created a pool to transmit to many others, Ellis said.
On the bright side, there is only one variety of chikungunya, so once you catch it, you will not catch it a second time, unlike dengue, she said. So, as it spreads, it self-limits, as more and more of the population is immune, she explained.
Along with controlling mosquito breeding areas, it is important to protect oneself by making sure screens are fixed, wearing long sleeves and repellant and so forth, officials said. These measures help reduce the spread, even after a person is infected, because a mosquito has to bite an infected person to spread it, said Dr. Marc Jerome, territorial medical director.
The chikungunya illness has spread throughout the Caribbean and, after the first case was confirmed in the territory in June, Health asked the U.S. Centers for Disease Control and Prevention for assistance, Plaskett said. The CDC’s team of epidemiologists and entomologists helped the Health Department with surveillance; diagnostic testing; data analysis and reports tracking the outbreak and response; public education; collecting mosquito specimens in both health districts to identify which species are in the territory and the role these mosquitoes play in transmitting the chikungunya virus and in many other ways, according to Plaskett.
The CDC team found high populations of the Aedes aegypti mosquitoes in homes and dwellings in the territory and, as a result, recommended a strategy of public outreach, source reduction and education on personal protection as a primary method of prevention and control.
According to Plaskett, the CDC’s arboreal experts and vector control specialists say the most effective method of abatement for Aedes aegypti mosquito in the territory is to reduce the source of breeding elimination by draining and dumping stagnant water from containers like buckets, pet dishes, flower pots and tires. Adding larvicide to large bodies of stagnant water that cannot be drained or dumped, eradicating mosquito eggs/larval before they become adult with a bacterial insecticide known as Bti briquettes or mosquito dunks are also recommended, she said. The department is working with schools and others to seek out and eliminate breeding sources, she said.
According to the Health Department, everyone can help to mitigate the spread of chikungunya by doing the following:
– Use insect repellents containing DEET or oil of lemon eucalyptus. Apply repellent only to exposed skin or clothing, and follow product instructions carefully. Do not use repellents on babies less than 2 months of age;
– Use air conditioning or window/door screens to keep mosquitoes outside. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net;
– Wear clothing that protects you from mosquito bites, such as long-sleeved shirts and long pants;
– Protect infants: cover cribs, strollers and baby carriers with cotton mosquito netting at all times, day and night, both inside and outside of your home. Dress babies in loose cotton clothing that covers arms and leg;
– Treat clothing with permethrin or purchase permethrin-treated clothing.
Now that school is back in session, outreach activities will reconvene for school beginning with focus on daycares, kindergarten and elementary schools, Plaskett said. The V.I. National Guard has also volunteered to help with outreach and source reduction efforts, she said.
Health recommends anyone who thinks they may have chikungunya to first seek medical care at a local health clinic or their primary care medical provider to reduce any potential overburdening of the hospital emergency rooms.
Seek emergency medical attention only if you develop any of the following symptoms: neurologic symptoms including irritability, drowsiness, severe headaches or sensitivity to light; chest pain, shortness of breath, or persistent vomiting; fever persisting for more than five days; intractable severe pain, extreme weakness, cold extremities or cyanosis; decreased urine output and bleeding under the skin or through any orifice; women in the last trimester of pregnancy, newborns and people with underlying diseases or weakened immune systems that are feared to be infected with chikungunya.
Anyone interested in assisting with community outreach and public awareness education can contact the department directly 340-773-1311 ext. 3171.
Community businesses interested in coordinating training and education for their onsite maintenance/facilities staff on administering larvicide and eliminating standing water sources should call DOH 340-773-1311 ext. 3171. Contact the DOH Environmental Health unit directly for onsite water source inspection and treatment at 340-774-9000(STT/STJ).
For more information about chikungunya, visit the CDC website at http://www.cdc.gov/chikungunya/prevention/index.html.