A record number of mosquitoes in and around Las Vegas carry the West Nile virus, prompting warnings from local health officials who say the public should take precautions to avoid being bitten.
West Nile virus can cause fever, headaches, vomiting and diarrhea and is fatal in about 1 in 150 cases. There are no vaccines or medications to treat or prevent disease transmitted by mosquitoes.
In recent weeks, 169 of more than 24,000 groups of mosquitoes tested for West Nile virus have returned positive — meaning at least one insect in the group carried the disease — in 25 Southern Nevada ZIP codes. The number of mosquitoes registered and the count of positive outbreaks at the beginning of the season break the area’s records for both metrics, set in 2019.
“This is a huge number of mosquitoes and we have already identified a concerning number of them carrying West Nile virus,” said Vivek Raman, environmental health supervisor for the Southern Nevada Health District.
Health officials also identified six pools in the Las Vegas area that tested positive for the St. Louis encephalitis virus, a mosquito-borne disease that can cause fatal inflammation of the brain.
For decades, climate scientists and public health officials have warned that climate change could expand the reach of various infectious diseasesespecially those spread by mosquitoes. The explosion of the mosquito population in Las Vegas and the local increase in prevalence in West Nile offer an important case study in how climate can affect human health.
Climate change increases global average temperatures and precipitation levels, promoting ideal conditions for mosquitoes, which breed in still, warm waters. It also prolongs the duration of hot periods, prolonging the mosquitoes’ active season. These changes increase the risk of human exposure to diseases such as West Nile virus, even in places that have never recorded cases before.
The first case of West Nile virus in Las Vegas was recorded in 2004 – five years after the first U.S. case was documented in 1999 in New York City. The most recent West Nile outbreak in Las Vegas occurred five years ago, resulting in 43 human cases. District health officials are worried this summer could be much worse.
In Nevada and much of the Southwest, spring weather get hotter and summer heat waves have become increasingly extreme in recent decades. Las Vegas had average spring temperatures has increased by 6.2 F since 1970; this month, the city has already experienced a week-long record heat wave.
Rising temperatures in Southern Nevada are creating favorable conditions for mosquitoes, said Nischay Mishra, assistant professor of epidemiology at Columbia University. Furthermore, continued drought conditions in the state, which have led to low water tables throughout the Colorado River Basin, including in Mead Lakeit may also be counterintuitively beneficial to insects.
“Mosquitoes normally thrive in moist and warm places,” Mishra said. “But in Nevada, as smaller bodies of water dry out, shallow waters are created that are ideal for mosquito breeding.”
The mosquito surge in Las Vegas has been massive: Last year, district health officials measured 6,000 mosquitoes in traps throughout Clark County from April through June. This year, counts have already surpassed 24,000.
The vast majority were Culex mosquitoes, a primary vector of West Nile virus. But another species of mosquito that does not transmit the virus, Aedes aegypti, has also become more common in Las Vegas. Aedes was first spotted in the area in 2017, and Raman also attributes its spread there to the impacts of climate change.
Along with climate, human behavior plays an important role in the spread of vector-borne diseases. Aedes and Culex mosquitoes thrive in the backyards of many Las Vegas homes — the former breed in small puddles of water, like those left by sprinklers, while the latter often breed along the surface of unmaintained swimming pools.
Raman said the best way to avoid infection is to empty any open containers filled with water outside, maintain swimming pools, wear protective clothing and repel insects to avoid being bitten.
Louise Ivers, professor of global health and social medicine at Harvard Medical School and director of the Institute for Global Health, said situations like the one in Las Vegas will become more common as climate change continues to increase infectious diseases around the world. .
“We should expect to see new infectious diseases, old infectious diseases come back, and a change in exposure patterns of existing infectious diseases like West Nile virus,” Ivers said. “Things that we used to do freely, without worrying so much about protection against vectors like mosquitoes or ticks, we may no longer be able to do.”
This article was originally published in NBCNews. with
