Heatstroke, Mosquitoes, and West Nile Virus

Heatstroke, explained 

Heatstroke is when the body's internal temperature has climbed to 104°F or higher for a sustained period, and the body has lost its ability to cool itself. Without rapid treatment—typically an ice bath, placing ice packs in key regions of the body, or other cooling steps—it can result in multiorgan failure and death. 

It's the top cause of US death in natural disasters, and mounting research shows that more extreme heat days are putting Americans at elevated risk of developing heatstroke and other heat-related illnesses. Young children and the elderly are particularly at risk because their bodies are not as adept at regulating heat. But exertional heatstroke from exercising in extreme heat is a leading cause of death among athletes and soldiers in training. 

When the body can no longer cool itself, in the short term that can lead to cell degradation and an inflammatory response that damages organs, including the kidneys, liver, and brain. Recent research also furthers the idea that this condition causes longer-term epigenetic changes that predispose people to future health complications.

Explore everything else we've found on Heatstroke.

Also, check out ... 

> Extreme heat is neurologically impairing animals. (Read)

> How the gut microbiome can affect heatstroke risk. (Read) 

> Heatstroke can reprogram your DNA, putting survivors at risk of future health problems. (Read) 

> Hundreds of vulnerable Chicago residents died in 1995 during a long-lasting heat wave. (Watch) 

> Few states mandate heat guidelines for school athletes, and that's of increasing concern with more high-heat-index days. (Read)

> Heatstroke treatment guidelines were built almost exclusively on research in men. (Read) 

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A bite-sized mosquito explanation 

Mosquitoes kill more people than any other animal in the world: about 760,000 people annually. Though there are more than 3,500 species of mosquitoes, and only a very small fraction of them bite humans, the diseases they carry can be deadly. Malaria, dengue, West Nile virus, and more sicken and kill humans and other animals, too. Only females bite humans, and they suck our blood because they need blood proteins to sustain their eggs. 

The bugs have been spotted on every continent but Antarctica. Their range is expanding with climate change, and mosquitoes were most recently documented in 2025 in Iceland, the last mosquito-free country until that point. Even as mosquitoes spread to new locales and the bugs develop resistance to insecticides, scientific advances are creating new mosquito control options. 

Gene-editing technology could now theoretically render female mosquitoes infertile to wipe out disease-carrying species, though concerns remain about effectively limiting this engineered trait to the target species. Infecting mosquitoes with the Wolbachia bacterium is another option under consideration, since the naturally occurring microbe blocks transmission of various diseases.

Explore everything else we've found on Mosquitoes.

Also, check out ... 

> Mosquitoes even have olfactory receptors on their sperm. (Watch) 

> How we helped make Aedes aegypti mosquitoes such a problem. (Watch) 

> Iceland, the last mosquito-free country, detected them in 2025. (Watch)

> Disney World is largely mosquito-free, thanks to civil engineer Joe Potter. (Watch) 

What's West Nile virus?

West Nile virus primarily affects birds and is spread via mosquito bites. Yet the virus can make the jump to humans when infected mosquitoes bite us. Though humans aren't typically symptomatic, roughly one in five infected people feel sick from the virus, and it rarely causes severe, life-threatening brain health complications, including encephalitis and meningitis.

The virus was first identified in the blood of an infected human in Uganda in 1937 and soon hopscotched to Europe. It wasn't detected in the US until the summer of 1999, when it caused a human outbreak and killed nearly 5,500 crows in just four months. The virus has spread widely and is found in 48 US states. Beyond humans, birds, and mosquitoes, the virus has mostly been detected in horses.

There are vaccines to protect birds and horses, but none for humans. The lack of a market for a human vaccine—since so many people are asymptomatic—is one major development hurdle. But in 2025, the US experienced a 40% spike in its West Nile human caseload, due in part to warmer temperatures and increased rainfall. More than 1,400 people had severe infection complications.

Explore everything else we've found on West Nile Virus.

Also, check out ... 

> How a scientist discovered West Nile is spread by birds. (Watch)

> West Nile is maintained in nature, even without infecting humans. (Listen)

> There's a West Nile virus prevention rap—and it's amazing. (Watch)

> Horses can get West Nile, but unlike humans, they have vaccines available. (Read)

 Medical Developments Spotlight 

We love spending time learning about the latest medical breakthroughs and spotlighting research that piques our interest, may influence future research directions, or inform healthcare conversations. Here's what we found this week.

> Experimental weight-loss drug leads to 30% body weight loss in obese patients 

Good Morning America | Liz Neporent and Shafiq Najib. Results from a late-stage clinical trial by Eli Lilly and Company include that its experimental weight-loss drug, retatrutide, led to an average weight loss of 70.3 pounds over 80 weeks in patients with obesity. What's more, 45% of the most obese patients taking the highest dose, a once-weekly injection of 12 milligrams, lost 30% or more of their body weight. The drug targets three hormone receptors and isn't yet FDA-approved. The company released the latest clinical trial findings, but they haven't been published in a peer-reviewed journal. (Read) 

> Hospital wastewater can reveal deadly fungal problems months before symptoms 

2 News Nevada | Staff. Drug-resistant strains of Candida auris are detectable in wastewater up to five months before patients get sick, suggesting that routinely monitoring hospital sewer lines could avert potentially deadly hospital outbreaks of this fungal pathogen. The research comes as Nevada is experiencing the largest recorded outbreak in the US since 2022, with more than 1,600 people reportedly sickened in the state last year. (Read) 

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Best of the Week

We curate hundreds of resources into 1440 Topics each week. Here are some of our favorites from the world of health and medicine.

> What to know about Bundibugyo virus, a species of Ebola causing an outbreak.

> Climate shifts in Argentina set the stage for the hantavirus cruise ship outbreak. 

> Listen to the evolving economics of prosthetics.

> Hookworm infection may help fight certain autoimmune conditions.

> How historical outbreaks at sea helped shape global public health.

> Read why running is also a mental sport. (More on exercise.)

> Hear the wild story of America's food safety in the 19th century.

> Grief retreats are becoming more common. 

> What to know about life-threatening sepsis.

> Learn about the fertility crisis and why we should care about the global baby bust.

> Drugged-driving research has languished with government cutbacks. 

> Disembodied human brains are being used for drug testing.

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