Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Incidence of Tick- and Mosquito-Borne Illnesses Growing Rapidly

Dear Doctor: It seems like every time I turn on the news someone's freaking out about ticks and mosquitoes. Haven't they always been around? What's with the alarm bells all of a sudden?

Dear Reader: The reason you're hearing so much about ticks and mosquitoes these days is because of a worrisome spike in the number of people becoming infected with the range of diseases these creatures cause. (We can't say "insects" because, while mosquitoes do fall into that category, ticks don't. They're actually arachnids -- like mites, spiders and their larger cousin, the scorpion.) According to a report released by the federal Centers for Disease Control and Prevention in May, the incidence of disease spread by ticks and mosquitoes has more than tripled between 2004 and 2016.

In just 13 years, the number of tick- and mosquito-borne illnesses in the United States has ballooned from 27,388 reported cases in 2004 to 96,075 reported cases in 2016. Even more concerning is the fact that more than half of that increase occurred between 2015 and 2016. And the key word here is "reported." Not every tick- or mosquito-borne illness is identified or gets reported, so the number of people made ill by a tick or mosquito bite is quite likely higher. (The CDC's report also covers fleas, with a total of 89 reported cases of plague over the 13 years of the report.)

Lyme disease accounted for 82 percent of the increase in tick-borne illness, according to the report. A closer reading of a breakout of the data reveals some troubling trends. For example, babesiosis, a malaria-like illness carried by deer ticks, went from zero cases in 2010 to more than 1,900 reported cases in 2016. Anaplasmosis, also caused by a bacterium carried by the deer tick, jumped more than 650 percent, from 875 cases in 2004 to 5,750 cases in 2016. If left untreated, the disease can cause internal bleeding, difficulty breathing, neurological problems and kidney failure.

When it comes to mosquitoes, the report offers both good and bad news. Cases of Zika have gone from zero in 2015 to 41,680 the following year. Virtually all were reported in Puerto Rico, American Samoa and the U.S. Virgin Islands. West Nile virus, meanwhile, which hit a high of 5,674 cases in 2012, dropped by half by 2016. In addition, the CDC reports that nine new germs that are spread by ticks and mosquitoes have been identified since 2004. Scientists say the rise in disease rates, as well as the widening of their geographic scope, is due in part to the warming climate, which expands the pests' habitats. Global trade and travel also play a role.

Our aim here is not to alarm, but to stress the importance of vigilance in protecting yourself and your family. Bottom line: Create a barrier between yourself and the potential threats. That means appropriate clothing to cover you when spending time outdoors, bug repellent for a chemical shield, and regular visual checks of your skin, scalp and clothing. And don't forget about the pets -- a range of excellent meds are available to keep your furry companions tick- and flea-free as well.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)