by A record number of mosquitoes in and around Las Vegas are carrying the West Nile virus, prompting warnings from local health officials who say the public should take precautions to avoid biting them.
West Nile virus can cause fever, headache, vomiting and diarrhea and is fatal in about 1 in 150 cases. There are no vaccines or medications to treat or prevent the mosquito-borne illness.
In recent weeks, 169 of more than 24,000 pools of mosquitoes tested for West Nile virus — meaning at least one insect in the pool had the disease — across 25 southern Nevada ZIP codes. The number of mosquitoes recorded and the number of positive pools this early in the season break area records for both metrics, set in 2019.
“These are a large number of mosquitoes, and we’ve already identified an alarming number that have West Nile virus,” said Vivek Raman, environmental health supervisor for the Southern Nevada Health District.
Health officials also identified six Las Vegas-area swimming pools 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 range of various infectious diseases, especially those spread by mosquitoes. Las Vegas’ explosive mosquito population and the local uptick in West Nile prevalence provide an important case study of how climate can affect human health.
Climate change increases average global temperatures and precipitation levels, which creates conditions suitable for mosquitoes, which still breed in warm water. It also extends the duration of hot periods, extending the active season for mosquitoes. These changes increase the risk of human exposure to diseases such as West Nile virus, even in places where cases have never been recorded before.
The first case of West Nile virus was recorded in Las Vegas in 2004 – five years after the first US case was documented in 1999 in New York City. The most recent West Nile outbreak occurred in Las Vegas five years ago, resulting in 43 human cases. Area health officials are concerned that this summer could be much worse.
In Nevada and much of the Southwest, spring weather has been getting warmer and summer heat waves have become more extreme in recent years. Average spring temperatures in Las Vegas have risen 6.2 F since 1970; this month, the city has already experienced a week-long heat wave.
Southern Nevada’s rising temperatures are creating favorable conditions for mosquitoes, said Nischay Mishra, an assistant professor of epidemiology at Columbia University. In addition, persistent drought conditions in the state, resulting in low water table levels throughout the Colorado Basin, including in Lake Mead, may be counterintuitively beneficial to the insects.
“Mosquitoes tend to thrive in wet and warm places,” Mishra said. “But in Nevada, as smaller bodies of water dry up, they create shallow waters that are great for mosquito breeding.”
The Las Vegas mosquito boom has been huge: Last year, district health officials measured 6,000 mosquitoes in traps across Clark County from April to June. This year, the number is already more than 24,000.
The vast majority were Culex mosquitoes, a primary vector for West Nile virus. But another species of mosquito that does not carry the virus, Aedes aegypti, has also become more common in Las Vegas. Aedes was first seen in the area in 2017, and Raman also attributes its spread there to the effects of climate change.
Along with climate, human behavior plays an important role in the spread of vector-borne diseases. Both Aedes and Culex mosquitoes thrive in the backyards of many homes in Las Vegas—the former breed in small pools of water such as those left from sprinklers, and the latter often breed on the surface of poorly maintained swimming pools.
Raman said the best way to avoid infection is to empty any open containers filled with outdoor water, maintain swimming pools, wear protective clothing and use bug spray to avoid biting.
Louise Ivers, professor of global health and social medicine at Harvard Medical School and director of its Global Health Institute, said situations like the one in Las Vegas will become more common as climate change continues to increase infectious diseases worldwide. The world.
“We should expect to see new infectious diseases, the return of old infectious diseases and a change in the exposure patterns of existing infectious diseases such as West Nile virus,” Ivers said. “Things that we used to do freely without worrying so much about protection from vectors such as mosquitoes or ticks, we might not be able to do anymore.”
This article was originally published on NBCNews.com
