Sicknesses from mosquito, tick, and flea bites have tripled in the United States, with just over 642,600 cases reported during the 13 years from 2004 through 2016. Nine new germs spread by mosquitoes and ticks were discovered or introduced into the United States during this time, according to the latest “Vital Signs” report by the Centers for Disease Control and Prevention, CDC.
“Zika, West Nile, Lyme, and chikungunya – a growing list of diseases caused by the bite of an infected mosquito, tick, or flea – have confronted the U.S. in recent years, making a lot of people sick. And we don’t know what will threaten Americans next,” said CDC Director Robert Redfield, M.D
In addition, the number of mosquito “disease danger days” is increasing across much of the country as temperatures rise, representing a greater risk for transmission of mosquito-borne diseases, finds new research by the New Jersey-based science and advocacy group Climate Central.
To examine the role temperature is playing in disease transmission from mosquitoes, Climate Central analyzed the number of days each year in the spring, summer, and fall with an average temperature between 61 degrees and 93 degrees Fahrenheit. This is the range for transmission of diseases spread by mosquitoes of the Aedes type.
Of the 244 cities analyzed, 94 percent are seeing an increase in the number of days with temps between 61 and 93, indicating a heightened risk for disease transmission, or “disease danger days.”
Both types of mosquitoes transmit West Nile virus, with cases in all 48 continental states since its introduction to the United States in 1999. Aedes mosquitoes carry other dangerous diseases such as dengue, Zika, chikungunya, and yellow fever.
In order to transmit disease, a mosquito must bite twice – once to acquire the disease and a second time to pass it on. The largest number of these twice-biting mosquitoes are produced at 75 degrees Fahrenheit.
Three California cities rank numbers two, three, and nine on the list of biggest increases in disease danger days. Other cities in the top 10 list include southern and southwestern cities like Las Cruces, New Mexico, El Paso, Texas and Tucson, Arizona, where temperatures are suitable for mosquito survival and some disease transmission already occurs.
The Climate Central analysis suggests that since the 1970s, the risk of disease transmission in these cities has been increasing due to rising temperatures.
A few northern cities also make this list of greatest increases in disease danger days, including Helena, Montana, and Erie, Pennsylvania.
Climate change may make some locations too hot for mosquito survival and disease transmission. For example, there are fewer disease danger days in Phoenix since 1970. This is likely because the number of days above 95 degrees Fahrenheit in Phoenix is also going up, and 95 degrees is beyond the range of disease transmission.
Out of the 244 cities in the analysis, only 12 are seeing a decrease in the number of disease danger days during this time period.