How mosquitoes find you and other surprising health discoveries

Alzheimer’s, ringworms and mosquitoes all made news recently in medical journals and research labs. The findings pack some surprises.
At its best — and a miserable best at that — mosquito bites itch. At their worst, worldwide, the flying pest can cause dengue, yellow fever, zika, West Nile virus and malaria. Bites from those carrying diseases are no joke. The World Health Organization considers mosquitoes the deadliest animal.
But how do they find their human snacks?
According to research from the University of California Santa Barbara published in the journal Nature, they “integrate information from many different senses across various distances.” One of those is infrared detection.
As a news release on the study explains, “Infrared radiation from a source roughly the temperature of human skin doubled the insects’ overall host-seeking behavior when combined with CO2 and human odor. The mosquitoes overwhelmingly navigated toward this infrared source while host seeking. The researchers also discovered where this infrared detector is located and how it works on a morphological and biochemical level.”
Fact is, the bugs don’t see well. And their chemical-sensing ability can be thrown off by a strong wind. But when they’re close to people, they feel the heat rising from skin. When the researchers added infrared radiation from a source at skin temperature to human odor and elevated carbon dioxide, the researchers discovered the mosquitoes “began probing as if they were searching for a vein.” They described infrared radiation as a “strong cue,” in conjunction with those other factors, though “infrared alone has no impact.”
The findings could help reduce the risk of illness from mosquitoes, the researchers believe.
“The team’s discovery could provide a way to improve methods for suppressing mosquito populations. For instance, incorporating thermal infrared from sources around skin temperature could make mosquito traps more effective. The findings also help explain why loose-fitting clothing is particularly good at preventing bites. Not only does it block the mosquito from reaching our skin, it also allows the IR to dissipate between our skin and the clothing so the mosquitoes cannot detect it,” the researchers reported.
People who have multiple sclerosis are much less apt to have the amyloid plaques that are markers of Alzheimer’s disease, according to recent research from Washington University School of Medicine in St. Louis.
And that may open doors to new avenues of Alzheimer’s prevention.
“Our findings imply that some component of the biology of multiple sclerosis, or the genetics of MS patients, is protective against Alzheimer’s disease,” Dr. Matthew Brier, assistant professor of neurology and radiology and the first author of the study, published in the Annals of Neurology, said in a news release. “If we could identify what aspect is protective and apply it in a controlled way, that could inform therapeutic strategies for Alzheimer’s disease.”
The release called the study “an example of clinical observations directly impacting research.” Dr. Anne Cross, one of Brier’s mentors and collaborators, had long treated patients who had MS, an immune disorder that attacks the central nervous system. She noticed that although many of her patients were old enough to be at risk of Alzheimer’s or even had a family history of the neurodegenerative disorder, they weren’t developing Alzheimer’s.
“I noticed that I couldn’t find a single MS patient of mine who had typical Alzheimer’s disease,” said Cross, the Manny and Rosalyn Rosenthal and Dr. John Trotter MS Center chair in neuroimmunology. “If they had cognitive problems, I would send them to the memory and aging specialists here at WashU Medicine for an Alzheimer’s assessment and those doctors would always come back and tell me, ‘No, this is not due to Alzheimer’s disease.’”
Brier, Cross and colleagues recruited 100 patients with MS to have their blood tested for biomarkers of Alzheimer’s, then compared the results to a control group of 300 people who didn’t have MS but matched them in terms of age, genetic Alzheimer’s risk and cognitive decline. Fifty percent fewer of those with MS had amyloid pathology compared to the control group.
Their research suggests that “something about the nature of MS itself” protects against Alzheimer’s disease, which they plan to continue to study.
JAMA Network this week recounted the discovery of a fungal rash, Trichophyton indotineae, that’s proving to be resistant to the frontline preferred treatments that are supposed to wipe it out. The article notes that T. indotineae that’s hard to cure has been seen for a while in India, Bangladesh and areas in south Asia and has been reported in Latin America, Australia, Asia and Canada. It was first seen in the U.S. in March 2023.
At least one of the cases didn’t involve someone who’d traveled, so it appears it could be here on a larger scale. The article said it suggested “community transmission within the United States.”
T. indotineae is a type of ringworm. Ringworm is described by the Centers for Disease Control and Prevention as one of the most common forms of fungal skin infections, “typically considered a mild though highly contagious nuisance.” T. indotineae, on the other hand, is easily spread and creates widespread, inflamed, itchy patches. And unlike ringworm that’s usually easily banished with over-the-counter antifungal ointments or oral prescription medication, this form’s often resistant.
As is the case with many drug-resistant infections, it’s likely that the way people manage treatment has helped the fungus change in ways that can make it hard to kill, similar to what has happened with many antibiotic-resistant bacterial infections. One physician quoted on the issue said ointments and creams to kill fungus and still the itching are used widely but “erratically.” Health experts believe that people have used corticosteroids and antifungal treatments much the way they used antibiotics in the past, stopping treatment too soon and allowing the products’ targets to evolve in ways that allow them to evade treatments over time.
Typically, that pattern leads to a need for stronger and stronger treatments that if not used properly or long enough eventually also lose their effectiveness.