As the world’s climates continue to change, scientists predict that mosquitoes will thrive in more places across the globe than ever. This is because insects are often more successful at higher temperatures.1 For example, in 2009, 22 cases of Dengue Fever were reported and confirmed in Florida. Before 2009, Florida had not had a confirmed case of Dengue Fever in over 40 years.2 Many other states have been experiencing the same phenomenon – infectious diseases that we thought were long gone are now returning to the United States. The reason—climate change . Three of the most prevalent diseases now in the U.S. are Dengue Fever, Lyme disease, and West Nile virus. All three of these diseases are transmitted through insects and are linked to temperature.3 Currently, a fourth disease carried by mosquitos is on the rise in South America and is predicted to spread to North America – the Zika Virus. This Zika virus has been causing somewhat of a panic due to its association with a large rise in babies born with the serious and sometimes deadly microcephaly, a neurological disease. 4
Zika Virus
Zika virus is caused by the bite of an infected mosquito, the same species of mosquito that carries Dengue Fever, and usually causes mild fever, rash, and muscle/joint pain. The Zika virus was first discovered in the Zika forest in Uganda in 1947 and had remained on the continent of Africa for several decades.5
However, people are growing concerned about Zika because it turns out that it can have far worse effects than simply a mild rash and fever. In 2015, thousands of babies in Brazil were born with abnormally small heads and brain damage. The condition is called microcephaly, and researchers believe Zika causes it.6
Microcephaly is typically caused by exposure to toxic substances during pregnancy, genetic abnormalities, or diseases during pregnancy such as herpes. Scientists know little about Zika, which until 2007 had only sporadically occurred in Africa and Southeast Asia since its discovery in 1947. However, scientists are discovering that Zika can cross the placental barrier and is linked to Guillain-Barre syndrome, which is an autoimmune disease causing paralysis. In 2015, Zika appeared in Brazil, Colombia, Mexico, and Puerto Rico.7
Scott Weaver, an expert on mosquito-borne viral diseases at The University of Texas Medical Branch, said, “By trying to diagnose more of these cases at birth by sampling cord blood, they may learn more about how these fetuses were infected.” 8
Dengue Fever
Dengue Fever is a mosquito-borne virus that affects approximately 40% of the world’s population. The virus is transmitted by the Aedes aegypti mosquito, which usually lives in tropical regions. However, warming surface temperatures have allowed this type of mosquito to expand its range into additional regions.9 What is puzzling to scientists, however, is that some areas in the U.S. with dengue-carrying mosquitoes have experienced outbreaks and some have not. For example, Key West, Florida has experienced numerous outbreaks of Dengue while Tucson, Arizona has not. Given that the dengue virus needs at lease eight days to incubate inside the mosquito, scientists believe, for example, in Tucson, the temperatures are too high and the humidity level is too low for the mosquitoes to survive long enough for the virus to incubate.10
This theory means cities will need varying mosquito-control programs to match their different climates. For instance, since the Aedes aegypti mosquito lives and breeds in close proximity to people – in gutters, flower pots, etc. – it is hard to control them using insecticides . Officials in Key West have developed an alternate plan to insecticides—releasing genetically modified male mosquitoes into the wild. These mosquitoes will have a gene that will cause them to die before reaching adulthood, but this gene will also be passed on to offspring. However, some are concerned with the potential effects that releasing genetically modified mosquitoes into the wild could have on the ecosystem.11
Lyme Disease
Two types of ticks found in the United States transmit Lyme disease—the deer tick and the western blacklegged tick. The deer tick resides in the Northeast, North-central, and Mid-Atlantic regions of the U.S., while the blacklegged tick lives on the Pacific coast. In most cases, ticks must be attached to the body for 36-48 hours before the Lyme disease bacterium can be transmitted. Most often, humans are infected through the bites of nymph ticks because they are much harder to see and subsequently remove than adult ticks. Nymphs are more active during the spring and summer months, while adult ticks are more active during the cooler months of the year.13
Lyme disease was first identified in the U.S. in 1975 in Lyme, Connecticut and has steadily spread since then. Tick control methods range from removing leaves and brush around houses to applying insecticide . Since there is a relationship between the abundance of deer and the abundance of deer ticks in the eastern U.S., methods such as putting up fences around houses and removing plants that deer eat have been used to control deer populations in populated areas.15 Like with the Aedes aegypti mosquito, ticks have been able to expand their range due to warmer temperatures. Since mice and deer are ticks’ two main hosts, the warming temperatures have allowed these species to expand their habitat ranges, therefore letting the tick expand its range as well.16
West Nile Virus
The West Nile virus was first documented in the West Nile district of Uganda in 1937. It was not until 1999 that a strand of West Nile that had been circulating in Israel and Tunisia was imported to New York. Since the first outbreak in the U.S., the West Nile virus has quickly spread and is now established from Canada to Venezuela. Outbreak sites usually occur along the migratory routes of birds, because feeding on infected birds’ blood is how mosquitoes become infected with the virus. In turn, infected mosquitoes then feed on the blood of healthy birds, infecting the birds and continuing the cycle. The type of mosquito most often associated with carrying the West Nile virus is the Culex Pipiens mosquito.17
Out of the people infected with West Nile, 80% show no symptoms. The other 20%, however, either develop West Nile fever or one of the more severe, neuroinvasive diseases, such as West Nile meningitis.18 Like with the Aedes aegypti mosquito, the deer tick, and the blacklegged tick, warmer temperatures have expanded the habitat range for birds and thus have also expanded the range of the Culex Pipiens mosquito.
Now that insect-borne diseases are on the rise, the best thing to do (aside from cutting down on greenhouse gas emissions , of course) is to protect yourself and your family from insect bites. The best way to reduce mosquitoes is to eliminate the places where they lay eggs, like artificial containers with standing water (pots, pet bowls, storage barrels, etc.). The Center for Disease Control also recommends using repellent on your skin, wearing long sleeves and pants, and making sure that screens are secure on doors and windows.
