Insects, Ticks and the Diseases They Carry

Mosquito-borne Diseases

West Nile virus, which is spread by mosquitoes, is less common than Lyme disease but can be significantly more dangerous.

West Nile virus has caused at least a thousand deaths since its arrival in the U.S in 1999, according to the U.S. Centers for Disease Control and Prevention. During that time nearly 28,000 cases of West Nile virus infection have been diagnosed, though most public health experts say many cases go unreported.

WNV can affect individuals of all ages. In 2007 a 3-month-old infant and a 99-year-old man contracted it. Twenty percent of those who contact WNV get quite ill. Some have lasting neurological damage.

For more on WNV, visit

Zika virus is an emerging mosquito-borne virus transmitted by Aedes mosquitoes, which bite primarily during the morning and late afternoon. It was first identified in Uganda in 1947 through a monitoring network of sylvatic yellow fever in rhesus monkeys, with the first reported case in humans occurring in 1952. Outbreaks of the virus have been recorded in Africa, Americas, Asia and the Pacific. Symptoms can include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headaches. Symptoms are also usually mild and last for 2-7 days.

While symptoms of the disease are usually mild, there are further potential complications which can result from the virus. During large outbreaks of the virus in French Polynesia and Brazil during 2013 and 2015, scientists observed a correlation between Zika and the rise of both Guillain-Barré syndrome and cases of microcephaly in newborns. This link along with others is still under investigation, with more and more information being discovered each day.

There is no vaccine currently available for Zika virus and preventative measures and caution should be taken when traveling to or living in infected areas. This can include using repellents which contain DEET, wearing long sleeved clothing, removal of water in open containers which can attract mosquitoes and limiting being outside during times when Aedes mosquitoes (the mosquito which is known to transmit the Zika virus) bite which is usually early morning and late afternoon.

For more information on Zika, visit:

Other mosquito-borne diseases in the U.S. cause infections in humans less frequently but they have devastating–often deadly--consequences. St. Louis encephalitis, eastern equine encephalitis and LaCrosse encephalitis are examples. Malaria and dengue, two tropical diseases are also reported in the U.S. Dengue is also prevalent in Puerto Rico, Hawaii and other popular offshore tourist destinations.

Lyme and Other Tick-borne Diseases

Mosquitoes, ticks and other insects can be annoying. But, being bothersome is a minor issue when compared to the serious diseases they can transmit. Here in the United States, the most common tick-borne disease is Lyme disease, spread by the deer tick.

Lyme disease has spread across the country to California, with more than 20,000 cases annually. Experts suggest that as many as ten times that number actually occur but are not diagnosed or reported.

Lyme disease is rarely fatal but can cause serious long-term health effects. If caught early, it is treatable with antibiotics. Contrary to popular lore, fewer than half of those with a Lyme infection develop the distinctive “bull’s-eye” rash around the site of the tick bite.

For more on Lyme, visit the American Lyme Disease Foundation’s Web site, You will find useful tips on locating ticks on your body and removing them. Different species of ticks are shown. Also see for extensive information on tick-borne infections.

Rocky Mountain spotted fever occurs throughout the U.S. from April through September. More than half of the cases occur in the southeast from Delaware to Florida, with highest incidence rates occurring in North Carolina and Oklahoma. Although this disease was first discovered and recognized in the Rocky Mountain area, relatively few cases are reported there.