In a span of 13 years, diseases from mosquito, tick, and flea bites have more than tripled in the United States with over 640,000 cases since 2004.

During the same period until 2016, nine new germs carried by mosquitoes and tick have been introduced in the country, according to the latest findings published in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.

CDC examined 16 vector-borne diseases caused by mosquitoes, ticks, and fleas. The data were from the National Notifiable Diseases Surveillance System. However, analysts say not all cases were reported, so it is difficult to measure the overall cost and burden of these diseases.

"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 Dr. Robert Redfield.

Lyme disease, ehrlichiosis, and anaplasmosis are the most common illnesses caused by tick bites. During the study period, the authors noted that tick-borne illnesses comprise 77 percent of all vector-borne disease case reports. Lyme disease, on the one hand, accounted for 82 percent of all tick-borne diseases.

Redfield urged state and local health departments to intensify their programs in fighting vector-borne diseases.

Climate Change: A Factor For Vector-Borne Infections

Dr. Lyle Petersen, the agency's director of vector-borne diseases, said that "the numbers on some of these diseases have gone to astronomical levels."

The report cited that increased overseas travels and commerce have contributed to the rise of infections caused by vector pathogens. For example, a traveler may be unknowingly infected by Zika in one country and then carries that same disease back home.

Petersen neither attributed these vector-borne diseases to climate change nor did the report mention the issue.

"The mosquito-borne diseases tend to get worse during heat waves," Petersen explained. "Increasing temperatures tend to make mosquitoes more infectious and infectious faster, thus promoting outbreaks. For tick-borne diseases, increasing temperatures will tend to expand the range of these ticks further north as well as increase the length of the tick season."

Dr. Paul Auwaerter, president of the Infectious Diseases Society of America, said they are investigating how climate change influences the spread of vector-borne diseases in their goal to protect public health.

He also urged the Congress to increase funding allocations for programs related to the surveillance and prevention of vector-borne illnesses, including research efforts about tick-borne infections.