The 2024 CAC Florida Climate Conference will focus on Climate and Human Health. This year’s event will be held November 14-15, 2024, in the brand new conference facility at the University of South Florida, Sarasota-Manatee campus. Vector-borne disease will be one of the many topics we will discuss and it’s making news headlines this week.
Mosquitoes are considered by many as the deadliest creatures on the planet, transmitting diseases such as West Nile, dengue, malaria, chikungunya, yellow fever and Zika.
A growing body of research has found that climate warming is expanding the geographic range for certain insects—and the diseases they carry.
Right now in Las Vegas, a record-breaking number of mosquitoes in the Las Vegas region are testing positive for carrying West Nile virus. This has caused warnings from local health officials urging the public to take precautions to avoid getting bit.
It’s happening much farther north too. Mosquitoes found in the city of Chicago, Highland Park, and Skokie have tested positive for the West Nile virus already this summer. Last year, 119 human cases of West Nile virus and six deaths were reported in Illinois.
Climate scientists and public health officials have warned for decades now that climate warming could expand the reach of various vector-borne diseases, especially those spread by mosquitoes.
What is a vector-borne disease?
Vector-borne diseases are human illnesses caused by parasites, viruses and bacteria that are transmitted by vectors.
Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans. Many of these vectors are bloodsucking insects, like mosquitoes.
The vectors ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host. Once a vector becomes infectious, they are capable of transmitting the pathogen for the rest of their life during each subsequent bite/blood meal.
Climate warming’s role
Climate warming can increase the spread of vector-borne diseases by creating more favorable conditions for vectors, such as mosquitoes, ticks, and fleas, to thrive.
Warmer temperatures can speed up the life cycle of these vectors, increase their population size, and widen their geographical range. Additionally, climate change can alter rainfall patterns and increase humidity levels, creating ideal breeding conditions for vectors.
It also extends the length of warm periods, prolonging the active season for mosquitoes.
These changes can result in more people being exposed to vector-borne diseases like West Nile virus, malaria, dengue fever, Lyme disease, and Zika virus, even in places that have never recorded cases before.
The situation in Las Vegas
Las Vegas’ exploding mosquito population and the local uptick in West Nile prevalence offers an important case study on how climate warming is affecting human health.
The number of mosquitoes testing positive for the disease this early in the season breaks the area’s records for both metrics, set in 2019.
Health officials in the Las Vegas area have also tested some mosquitoes positive for St. Louis encephalitis virus, a mosquito-borne disease that can cause fatal inflammation of the brain.
Las Vegas had its first case of West Nile virus in 2004. This came just five years after the United States had its first case in 1999 in New York City. Las Vegas’ most recent West Nile outbreak occurred five years ago, resulting in 43 human cases. District health officials feat that this summer could be far worse.
The mosquito surge in Las Vegas has been enormous. Last year, district health officials measured 6,000 mosquitos in traps across Clark County from April to June. This year, counts have already exceeded 24,000.
Mosquitos in Florida
Four Florida mosquito species, are important vectors of human disease and are common around homes throughout the state. They are the yellow fever mosquito, the Asian tiger mosquito, the southern house mosquito and the common malaria mosquito.
The yellow fever mosquito and Asian tiger mosquito are daytime biters.
The Asian tiger mosquito is more aggressive and most active in the early morning and late afternoon. The southern house mosquito is primarily active at dawn, dusk and nighttime, though it will also feed during the day. All three species lay their eggs in standing water in pots, abandoned tires, pet dishes, toys, ditches and untreated pools.
The malaria mosquito bites at dawn, dusk and night, and prefers to breed in freshwater streams, ponds and lakes.
Mosquitoes aren’t the only nuisance biting insects in Florida. Biting midges, also known as “no-see-ums,” can also be an annoyance, especially in the morning and evening.
Biting midges are extremely annoying, but none are known to transmit disease agents to humans in the U.S. They have a much greater impact on animals, both as biting pests and vectors of disease agents. In North America, the most important disease agent transmitted to animals by biting midges is Blue Tongue virus.
These maps show the number of months when Florida temperatures are suitable for the yellow fever mosquito to transmit viruses that cause its vector-borne diseases. (Credit: Sadie J. Ryan)
Most concerning vector-borne diseases in Florida
Dengue and malaria are particularly important in Florida. The pathogens that cause these potentially lethal illnesses can be spread by local mosquitoes.
Florida tends to experience small annual outbreaks of dengue, with five locally acquired cases in Miami-Dade and Pasco Counties reported so far in 2024. The yellow fever mosquito and the Asian tiger mosquito are capable of transmitting the viruses that cause dengue.
Florida experts say see your doctor if you experience a sudden, horrific fever and purple rash, and ask if you could have dengue.
The malaria mosquito, as aptly named, can transmit malaria in Florida. In 2023, seven malaria cases in the Sarasota area were the first cases acquired within the state since 2003 and triggered a statewide alert.
While more rare in Florida, West Nile virus, St. Louis encephalitis and eastern equine encephalitis are severe illnesses that can spill over from infected animals to people and may cause severe neurological symptoms.
The yellow fever mosquito can spread chikungunya, yellow fever and Zika. Florida’s first locally acquired cases of chikungunya were reported in 2014, with no known cases since then. The yellow fever virus is not consistently present in Florida, and transmission of Zika virus has been limited since the 2016 outbreak, according to University of Florida.
How to protect yourself
Most mosquito bites are relatively harmless. The itchy bumps often last for just a day or two after a mosquito has punctured your skin. But if the mosquito is carrying certain germs, like viruses or parasites, these pathogens might enter your blood during the bite and make you sick. It can even be fatal.
The best way to avoid infection is to dump out containers, tyke toys, plant pots, kiddie pools, and other small areas in the yard that can hold water can really help control a lot of mosquitoes around your residence.
Avoid peak mosquito hours. Mosquitoes are most active during dawn and dusk. If possible, stay indoors during these hour.
If you must or choose to be outside during peak times, wear protective clothing and use bug spray to avoid getting bit.
Repellants such as DEET and picaridin can help boost personal protection. DEET is considered safe by many health organizations, including the U.S. Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA), when used as directed.
However, it should not be used on infants under two months of age and should be used with caution on children and pregnant women. DEET can cause skin irritation in some people, and it should be washed off the skin once it’s no longer needed for protection.
Follow the label instructions. Some parents choose to only spray their children’s clothing and strollers rather than applying repellants directly to their skin.
The CAC is committed to the climate conversation. We do this with events like the Climate Champions Awards Ceremony, Hurricane Season Forecast Day and the upcoming Annual Climate Conference in November, that will focus on human health. We also give climate presentations, focused on adaptation strategies, to thousands of people throughout the year.
You can support us in helping our conversation going by making a donation or becoming a member.