Mosquito ‘Danger Days’ Multiply as Climate Warms

This female mosquito (Aedes aegypti) has filled up on human blood, May 23, 2012. (Photo by Stephen Ausmus / USDA)


PRINCETON, New Jersey, August 14, 2018 (ENS) – 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.

This is CDC’s first summary examining data trends for all nationally notifiable diseases caused by the bite of an infected mosquito, tick, or flea. It provides detailed information on the growing burden of mosquito-borne and tickborne illnesses in the United States.

This female mosquito, Aedes aegypti, has filled up on human blood, May 23, 2012. (Photo by Stephen Ausmus / USDA)

“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.

“Our nation’s first lines of defense are state and local health departments and vector control organizations, and we must continue to enhance our investment in their ability to fight against these diseases,” Redfield said.

The report found that the nation needs to be better prepared to face this public health threat.

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.

Even though mosquitoes are often just an itchng irritation, the consequences can be deadly.

Two species of mosquito, Aedes aegypti and Aedes albopictus, carry dangerous diseases and tend to be found in the South and Southeast, though the Aedes aegypti’s range extends into California and the range of Aedes albopictus extends northeast to New York and New England and has the potential to exist in the Midwest.

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.”

head net
Wearing a head net is a must for anyone exploring the Alaska woods in summer, July 6, 2010 (Photo by Travis)

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, while other mosquitoes transmit St. Louis encephalitis and eastern equine encephalitis viruses.

These diseases are more often found in U.S. territories like Puerto Rico than in the continental United States, but there has been limited transmission of Zika, dengue and chikungunya viruses in Texas, Florida and Hawaii.

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. Other northern cities that didn’t make the top 10 list but have a large increase in the number of disease danger days are located in states such as Idaho, Vermont, Washington, New York and Michigan.

Of the possible 275 days analyzed for this report, Honolulu, Hawaii and San Juan, Puerto Rico fall in the disease transmission zone for the entire time period.

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.

Copyright Environment News Service (ENS) 2018. All rights reserved.


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