It can carry life-threatening diseases. It’s difficult to find and hard to kill. And it’s obsessed with human blood.
The Aedes aegypti is a species of mosquito that people like Tim Moore, district manager of a mosquito control district on the Western Slope of Colorado, really don’t want to see.
“Boy, they are locked into humans,” Moore said. “That’s their blood meal.”
This mosquito species is native to tropical and subtropical climates, but as climate change pushes up temperatures and warps precipitation patterns, the Aedes aegypti—which can spread Zika, dengue, chikungunya and other potentially deadly viruses—is on the move.
It’s popping up all over the Mountain West, where conditions have historically been far too harsh for it to survive. In the last decade, towns in New Mexico and Utah have begun catching Aedes aegypti in their traps year after year, and just this summer, one was found for the first time in Idaho.
Now, an old residential neighborhood in Grand Junction, Colorado, has emerged as one of the latest frontiers for this troublesome mosquito.
The city, with a population of about 70,000, is the largest in Colorado west of the Continental Divide. In 2019, the local mosquito control district spotted one wayward Aedes aegypti in a trap. It was odd, but the mosquitoes had already been found in Moab, Utah, about 100 miles to the southwest. Moore, the district manager, figured they’d caught a hitchhiker and that the harsh Colorado climate would quickly eliminate the species.
“I concluded it was a one-off, and we don’t have to worry too much about this,” Moore said.
Tim Moore, district manager of Grand River Mosquito Control District, explains that managing a new invasive species of mosquito in Grand Junction has required the district to increase spending on new mosquito traps and staff.Photograph: Isabella Escobedo
NEW YORK CITY (WABC) — The New York City Health Department is reporting the first human cases of West Nile virus this year.
The department says two residents in Queens have been infected, one was hospitalized briefly and discharged while the other remains hospitalization with encephalitis, an infection of the brain.
In addition, the virus was detected in blood donations from two individuals, one a resident of Brooklyn the other of Staten Island.
The virus has been found in mosquito pools across all five boroughs in the city since July.
Health officials spray regularly in neighborhoods to reduce the risk of mosquito activity.
They say mosquitoes infected with West Nile virus are typically present in New York City from May through October, with peak activity during August and September.
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Earlier this week, New York State health officials announced the death of an Ulster County man after he contracted eastern equine encephalitis, a mosquito-borne illness last detected in a New Yorker in 2015. EEE is fatal in 30 percent of human cases, there is no vaccine, and those who survive often face serious, long-term health effects. Every year, mosquitoes in at least two or three counties test positive for EEE, but so far this year, mosquitoes in 15 counties have tested positive. (Human cases have also been reported in New Jersey, Massachusetts, New Hampshire, Vermont, and Rhode Island.) Since its first recorded outbreak in 1938, which killed 25 people, Massachusetts has had more cases than any other state in the country, says state epidemiologist Dr. Catherine Brown. I spoke with Dr. Brown to get a sense of how dangerous EEE actually is, the role climate change plays in all of this, and how public-health officials are managing the backlash to mitigation recommendations after the COVID lockdowns.
So first, how does this thing spread? Migrating songbirds are what bring triple E into the state as they move northward. We have several very large swamp systems in Massachusetts that have both the birds and the mosquitoes that spread triple E to horses and people.
What constitutes an outbreak? Anytime we have more than one human case, we consider that an outbreak. At this point, we’re at four human cases and 96 positive mosquito samples. That is still quite a bit lower than what we had in 2019, when we had 12 human cases, six deaths, and almost 300 positive mosquito samples.
Is climate change going to make EEE outbreaks happen more frequently? We’ve seen a couple of changes in our historic pattern that I expect are at least partly due to climate change. In general, yes, we seem to be seeing cycles happening more frequently. We had a cycle in 2004 through 2006, and then we had another one in 2010 through 2012. So those were four years apart. Then we got a little bit of a nice break between 2012 and 2019, and now we’re back to four years.
That’s not the only change. In the 2004 to 2006 cycle, we had five cases. In the 2010 through 2012 cycle, we had seven. And then in 2019 and 2020, we had 12. So we’ve seen a steady increase in the effect on humans. I am concerned that that may also be a part of the climate-change effect. Also, before this year, all of those exposures occurred before September 15. I anticipate climate change is going to start moving that date further out.
Is climate change also why we’re seeing EEE pop up in more places this year? The geographic locations where we’re finding our most intense activity is very clearly changing. Southeastern Massachusetts in Bristol and Plymouth County has been our hot spot since 1938, when the first outbreak was recognized. But we have seen an expansion to other parts of the state. My suspicion is that there’s some change in the migratory bird pattern that is resulting in movement of the virus around the state. It’s hard to say.
I would imagine those birds in Massachusetts are the same ones that are flying over the swampier areas of Long Island or the Hudson Valley. The migratory birds bring triple E up from Florida in the spring. Some portion of them carries the virus up to Massachusetts and New York and New Hampshire and Maine. Once they bring it up, though, the amplification cycle that happens between birds and mosquitoes is going to vary by the individual area. It depends on how many bird species there are that year, how good the swamp habitat is, how much rain each swamp had, and also the size of the mosquito populations in those particular swamps that particular year.
So since the swamps play such an important role in all of this, will the changes in rainfall patterns have an effect on all of this in the future? The type of mosquito that bites the birds that carry the disease breed in swamps, in pockets of water that accumulate under tree roots. The more rain you have, basically, the more water is in those pockets, which is better for mosquitoes. But there’s a caveat. If it rains a lot — like a lot, a lot — after the mosquitoes have laid their eggs, it can actually flood out those pockets of water. When that happens, the eggs end up on top of the surface of the ground and they dry out, and that will actually reduce mosquito populations.So it’s complicated!
I’ve seen people warn that malaria could become a problem in the Northeast. Do you worry about that? Honestly, I spend much more time thinking about problems we have now that are very likely going to continue to be a problem, like West Nile virus and triple E. As we see increasing establishment of Asian tiger mosquito populations in the Northeast, it is possible that we could start to see increases in local transmission of malaria, dengue, chikungunya, and all the other viruses that people talk about. But unlike EEE, dengue is a disease of humans. There are no birds involved. In order for it to become a problem locally, we would need a relatively large influx of humans to become infected all at the same time.
Some states — including Massachusetts — have recommended that towns in areas where triple E has been detected in mosquito populations encourage residents to stay indoors after dusk. Is this the first time that municipalities have taken that kind of action? It is not the first time that’s happened. There’s actually been sort of a standing recommended public-health mitigation measure for communities that are at higher critical risk of triple E. I think it’s gotten a little bit more attention this year, because of how challenging the COVID shutdowns were for some people. And so I think this feels to some people as if it’s the same thing. But this predates the pandemic.
I heard a rumor that the state is considering withholding information about EEE-related deaths until the end of mosquito season. Is that true?Well, there’s a need to share information to help people understand what the public-health risk is, but we also want to make sure that we’re protecting patient confidentiality. So right now, we’re providing information about the sex of the person, their age range, and then the location where we think they were exposed to the virus. When you start to add additional information, like whether the patient was hospitalized or their current status, including whether they have passed away or not, it makes it easier to identify people. Also, triple E is a very significant infection. People don’t always just die or recover in a very short period of time. And so it often takes time to really understand what the outcome is of all of our patients.
In your personal life, as you step outside, do you think about EEE? Yeah, it’s a totally fair question. And so I will tell you that I actually live in an area that is at risk from EEE. And so the answer is yes, I absolutely do think about it. And I alter my activity based on EEE risk. I’m really careful about using mosquito repellent, and I don’t spend time sitting on my back deck where I would be a sitting target for those mosquitoes that could be carrying triple E.
So I have one of those unfortunate blood types that makes me extremely susceptible to mosquito bites. To give you a sense of how bad it is, I got attacked three times while installing the mosquito repellent system I’m reviewing here. Big, nasty, red welts that lingered for days.
I usually take extreme measures to avoid mosquitos, including topical products like OFF! and visits from a professional mosquito control company that sprays citronella all over my backyard every three weeks. Tragically, none of this has been of much help. For most of the summer, I look like Patient Zero for some kind of pox.
This summer I decided I’d had enough. Enter Thermacell’s LIV, an installed mosquito blocker system that can scale to fit your deck or yard, regardless of shape and size.
Invisible Force Field
LIV is not a mosquito-killing system—you’ll need zappers and poisons for that—but rather a repeller technology. It works based on a chemical called metofluthrin, which gives off a vapor that mosquitos apparently hate when heated. Metofluthrin isn’t unique to Thermacell; it’s also the active ingredient in OFF! mosquito lamps and wearable devices, among other products.
Photograph: Christopher Null
LIV is a wired system composed of two main components: a base station, called the Smart Hub, which calls the shots, and as many satellite Repellers as you need. The Smart Hub plugs into wall power and communicates via Wi-Fi with your home network. The Repellers are also wired, daisy-chained to the hub one after another via included cables.
If you’re imagining a low-voltage lighting system, you’re on the right track—only LIV isn’t quite as flexible. Each cable is a fixed 24 feet long—though shorter 10-foot cables are available as a separate purchase—since Repellers must be positioned about 20 feet away from one another. This is because the range of the vaporized metofluthrin is only 10 feet. With a ring of Repellers around your safe zone, you create an invisible anti-mosquito force field as a perimeter, with each Repeller’s coverage zone slightly overlapping.
Setup isn’t difficult, but it is time-consuming and requires some attention to detail. You may not have a lot of flexibility as to where to place the Smart Hub because it needs to reside near an electrical outlet and within the Wi-Fi range of your router—plus it has to be mounted on the wall. Since most homes have few exterior power outlets, finding the Goldilocks spot for the hub can be tricky.
Mosquitoes seen through a microscope in the Broomfield office of entomologist Michael “Doc” Weissmann, Ph.D. June 25, 2024.
Kevin J. Beaty/Denverite
Mosquitoes collected in Denver have tested positive for West Nile Virus, according to the city’s health and environment agency and the state health department.
So far this year, the Colorado Department of Public Health and Environment has confirmed seven cases in the state. Four required hospitalization, but none have died.
No human cases have yet been reported in the city and county of Denver, according to the Denver Department of Public Health and Environment. The state reported two cases this year in Arapahoe County, with one each in Delta, Jefferson, La Plata, Mesa and Weld counties, according to the state’s website.
Colorado recorded the year’s first human case of West Nile virus in an Arapahoe County resident last month — earlier than usual.
The city routinely tests adult mosquitoes for the virus from mid-June through mid-September by checking traps at five locations weekly across the city, according to the city’s health department.
Health providers can give supportive care to alleviate symptoms and aid recovery.
Anyone can contract it, but those older than 50 or with weakened immune systems are at higher risk of developing serious illness.
Symptoms may also include skin rashes and swollen lymph nodes, generally appearing three to 14 days after being bitten by an infected mosquito. Most infections are mild, but some cases are severe and it can be fatal. Those can lead to inflammation of the brain (encephalitis) or inflammation of the brain’s lining (meningitis), which can cause problems ranging from vision loss to paralysis, coma, tremors, and convulsions.
If you experience symptoms, health agencies say to consult a doctor.
Prevention, and avoiding mosquito bites, are key:
The bugs turn out from dusk to dawn, when it’s a bit cooler, often in the woods and in gardens.
Health officials suggest wearing long sleeves and pants and also applying insect repellent. More information can be found on the EPA’s website.
Also, be sure to drain standing water outside your home.
