The CDC reports that the number of cases of diseases spread by insects skyrocketed from 27,388 to more than 96,000 by 2016. Tick-borne diseases accounted for more than three-quarters of the total. “The relatively very large percentage of tick-borne cases, especially Lyme disease, was a little surprising,” says Ronald Rosenberg, a doctor of science in epidemiology who was research lead for the paper. “I knew how many cases we had, but seeing it all put together in the report made me realize that the tick that transmits Lyme disease, Ixodes scapularis, is really the most important vector in diseases in the United States today.” Paul Auwaerter, MD, clinical director in the department of infectious diseases at Johns Hopkins Medicine in Baltimore and president of the Infectious Diseases Society of America, agrees that Lyme disease has been the leading factor behind the increase. But he also points to a growing concern about mosquito-borne diseases. The number of cases reported jumped 73 percent in just one year, between 2015 and 2016, which officials attributed to the Zika virus, which is spread by mosquitoes. “We have history of [mosquito-borne diseases] in the United States,” Dr. Auwaerter says. “There’s some concern they might come with a vengeance with warmer climates.” RELATED: What Bit Me? Spot These 11 Bug Bites Auwaerter acknowledges that climate change may be a factor. “I think there’s always concern that potentially warmer temperatures will drive changes in insect and arthropod populations,” he says. “But it’s very hard to make a direct link to climate change. In the case of Lyme disease, there are many other factors that go into the mix.”
A Surge in Lyme Disease
The greatest increases in cases of Lyme disease have been reported in the upper Midwest and Northeast, but the disease has spread into southern Canada and states like Maryland and Virginia. Dr. Rosenberg attributes the rise to a number of causes. “One factor is that the tick lives in forested and shrubby areas, and people are continuing to move into suburbs, where there is proximity to forests and recreational areas,” he says. “This, along with increased outdoor recreation, is probably just putting people more at risk.” Another factor is the continued rise of the white-tailed deer population in much of the eastern part of the country. “The Ixodes scapularis is called the deer tick because the adult tick feeds on deer,” Rosenberg says. “The more deer you have, the more ticks you’ve got.” As more people travel around the world, the risk of spreading viruses to new territories rises. “West Nile virus was introduced to New York City around 1999,” says Rosenberg. “The same thing happened with the Zika virus, which we never had here before 2015. We’re not quite sure of the origin, but it was probably through a person who had the virus.”
New Diseases Identified
The CDC report lists nine vector-borne diseases that were reported in the United States for the first time between 2004 and 2016. In some cases, these diseases may have already been present but had not been identified as vector-borne in nature. “We are discovering indigenous diseases that have probably been here for a long time, and it’s likely that trend will continue,” says Rosenberg, who cites the tick-borne Heartland and Bourbon viruses as examples.
Steps to Prevent Bug Bites
The CDC offers several tips on preventing Lyme disease and mosquito bites. “For people who live in areas where there is Lyme disease and ticks, cover up and check yourself and your children and remove the ticks as soon as you find them,” Rosenberg says. “For mosquitoes, use repellent.” While education and prevention are key, Auwaerter stresses the need for other measures to help stem the tide of bug-bite diseases. “We’re still seeing more cases,” he says. “We need to think hard about alternative approaches that could be more effective. I think a vaccine would be the most valuable.”
