Here Come the Mosquitoes

It got me in March.

Maybe it happened while I was on a run, enjoying one of the first warm days of spring. Maybe I’d been waiting unsuspectingly for the train on an open-air platform. Maybe it happened in my own apartment. Regardless, at some point last month, I hesitated too long before brushing away a soft, fleeting sensation on my cheek. In the ongoing, 10,000-year-long game of tag between mosquitoes and humans, I’d taken another L.

Though it’s only early April, many New Yorkers have already gotten their first bites of the year: interviewer Isaac Fitzgerald and interviewee James Hannaham were driven out of a backyard by the bugs in Brooklyn; the city’s Department of Health has officially declared “it’s mosquito season in NYC!” and started tweeting out standing-water advisories; and CBS’ local affiliate recently ran a segment about how “it’s going to be a bad summer” for biting insects. Other metropolitan areas are also bracing for a buggy season ahead: “It’s looking like it’s going to be worse than it has [been in] the past two years,” Minnesota’s MPR News reports. “Epic rains expected to take one more swat at California, with masses of mosquitoes,” adds the Los Angeles Times. “We could possibly see more mosquitoes than we wanted to see,” a biologist warned the Ohio area.

Predicting the severity of mosquito season is a bit of an imprecise science, like trying to nail down a long-range weather forecast. Actually, it’s a lot like trying to nail down a long-range weather forecast, since mosquito populations fluctuate based on immediate and unreliable conditions, like spring rainfall and small changes in temperature. Generally speaking, more rain tends to precede “a greater prevalence of mosquitoes within the same month,” while “hotter temperatures [are] associated with increases in mosquitoes one to two months later,” reports one study, which focused on Dengue-carrying Aedes mosquitoes in Sri Lanka. (Invasive Aedes mosquitoes are also found on both U.S. coasts and throughout the South, with their habitats shifting north toward Chicago due to climate change.)

Mosquitos require standing water and temperatures steadily above 50 degrees Fahrenheit in order to start their breeding cycles. In the western United States, in addition to spring rainfall, natural occurrences of standing water are created by snowmelt, which causes floods that dry into perfect mosquito-breeding pools. Snowpack in the West, then, is one of the best early determinants of the coming mosquito season — unfortunate news for Californians, since their state broke a 40-year snowfall record over the winter. “Many places out west where they’ve received record rainfall and snowfall, they’re likely to have a very bad spring,” Daniel Markowski, the technical director of the American Mosquito Control Association, told Heatmap.

Snowmelt can also be a determining factor in the Midwest and East, where fears of spring flooding are already high. That said, their spring mosquito seasons are “less dependent upon the snow” than the West since they “always get at least some snow in many of the same areas,” Markowski went on. The bigger variable for the region is spring rainfall and how early it gets warm.

Mixed news on that front: NOAA expects the East Coast to be warmer than usual from April through June, with above-average precipitation concentrated around the Great Lakes region and potentially stretching south and seaward, through Pennsylvania, New York City, and the D.C.-area. Though the severity of the coming mosquito season is thus still a bit of an unknown, the stakes are high: Last year saw the largest number of ever recorded West Nile virus-positive mosquito pools in New York City, resulting in four deaths. There’s every indication that could happen again in 2023: “We expect mosquito and tick activity in NYC to be at similarly high levels,” M&M Pest Control, a Long Island City-based exterminator, writes on their website.

Warmer temperatures in the south and east could mean earlier emergences of mosquitoes.NOAA

Rainfall in most of the United States is expected to be normal this spring, but potential damp conditions around the Great Lakes and southern Acela Corridor could increase mosquito populations.NOAA

In the South, mosquito populations are “almost all rainfall- and temperature-driven” because snow is not the primary cause of standing water in the region, according to Markowski. While temperatures might not yet be high enough in the region for a major larvae boom, recent storms have authorities “concerned right now in southeast Mississippi, Alabama, Arkansas, Tennessee about mosquito populations,” Markowski said. Not to mention another reason for the South to be on high alert: Culex lactator, a species of mosquito native to South and Central America, has been discovered spreading throughout southwest Florida. Though it hasn’t been extensively studied, we do know Culex is a potential vector for West Nile and St. Louis Encephalitis.

Of especially high concern for infectious disease experts this year will be a place not usually thought of for its mosquitoes: Phoenix’s Maricopa County. Back in 2021, the region experienced the largest single outbreak of West Nile virus in U.S. history, likely due to a wetter-than-average monsoonal season; statewide, 127 people died. This year, winter snowmelt and spring rains have pulled the region out of its drought, but once the floodwaters start to recede, they’ll create major mosquito breeding grounds, NBC’s 12 News reports. The wetter desert environment will also attract more birds — the natural hosts of West Nile virus.

So while there is no guarantee that 2023 is going to be another “monster mosquito season” for the U.S. like 2021, there is no guarantee it won’t be, either. We know the West is unusually wet, which will almost certainly mean more bugs, while the Midwest and East are likewise tracking warm and damp. In the South, where storms are one of the biggest causes of standing water, there are fears that this year’s record number of early-season tornadoes is only a “prelude” of what’s to come.

That makes it all the more important to minimize mosquitoes where we do have some control: “What I try to get people to understand is, just as nature — rainfall, snowfall amounts; temperatures — impact mosquito problems, we have a lot of control over what bites us in our backyards,” Markowski said. “If we’re over-watering our property, or we’re allowing water to stand on our property, you’re making mosquitoes right there that bite you.”

Meanwhile, in New York City, the warmest days of the year so far are expected this week. Short-sleeved, sun-starved urbanites will be out in droves.

As will be mosquitoes.

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