That mosquito buzzing in your ear is not just one of summer’s annoyances. It’s also what epidemiologists call a vector, an organism that transmits a disease or parasite from one animal to another. While the bloodthirsty bugs are particularly good vectors, most of the diseases they carry are — or have been — a danger mostly in tropical and subtropical regions. But thanks to climate change and globalization, more pathogens are arriving on US shores. (For example, there is concern that chikungunya, a non-deadly flu-like virus that started cropping up in the Caribbean in 2013, will become more common in the United States as infected soccer fans return from World Cup games in Brazil.) Here’s what you need to know about the more common diseases the little buzzers carry.
WEST NILE VIRUS
STRIKES Humans, dogs, cats, horses, pet birds
SYMPTOMS Usually none, though about 20 percent of those infected experience flu-like symptoms
TREATMENT No specific treatment, but over-the-counter medicine can treat some symptoms; more severe cases may require hospitalization
MORTALITY/MORBIDITY Less than 1 percent may develop encephalitis or meningitis; one-10th of those people may die from the infection
CASES IN MASSACHUSETTS Hard to track because so many people have no symptoms or flu-like symptoms; between 2000 and 2010, 67 people in the state had severe symptoms, and six died; eight human cases were identified in 2013
EASTERN EQUINE ENCEPHALITIS
STRIKES Humans, dogs, cats, horses, pet birds; it is fatal to horses, and the National Institutes of Health is concerned the disease, while still rare, is spreading in New England
SYMPTOMS Mostly flu-like, but the encephalitic form of the virus can cause irritability, convulsions, and other symptoms
TREATMENT None for humans (there is a vaccine for horses)
MORTALITY/MORBIDITY Fatal in approximately 33 percent of human cases, with significant brain damage in most survivors
CASES IN MASSACHUSETTS Health officials confirmed four cases in horses and one in a human in 2013; the state has the second highest rate of human infection in the country, with 46 individuals sickened between 1964 and 2013
YOUR BEST DEFENSES
> Apply insect repellent on exposed skin and clothing when outdoors.
> Weather permitting, wear long-sleeve shirts, long pants, and socks outdoors.
> Be extra cautious during peak biting hours, from dusk till dawn.
> Close or use screens on windows.
> Reduce the number of mosquitoes around your home by emptying standing water in flowerpots, pool covers, pet water dishes, birdbaths, and so forth.