Health
When heat waves turns deadly: How extreme temperatures affect the human body
As temperatures and humidity soar outside, what’s happening inside the human body can become a life-or-death battle decided by just a few degrees.
The critical danger point outdoors for illness and death from relentless heat is several degrees lower than experts once thought, say researchers who put people in hot boxes to see what happens to them.
With much of the United States, Mexico, India and the Middle East suffering through blistering heat waves, worsened by climate change, several doctors, physiologists and other experts explained to The Associated Press what happens to the human body in such heat.
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Heat waves can raise your body temperature
The body’s resting core temperature is typically about 98.6 degrees Fahrenheit.
That’s only 7 degrees away from catastrophe in the form of heatstroke, said Ollie Jay, a professor of heat and health at the University of Sydney in Australia, where he runs the thermoergonomics laboratory.
Dr. Neil Gandhi, emergency medicine director at Houston Methodist Hospital, said during heat waves anyone who comes in with a fever of 102 or higher and no clear source of infection will be looked at for heat exhaustion or the more severe heatstroke.
A man pours cold water onto his head to cool off on a sweltering hot day in the Mediterranean Sea in Beirut, Lebanon, on July 16, 2023. As temperatures and humidity soar, what’s happening inside the human body can become a life-or-death battle decided by just a few degrees. (AP Photo/Hassan Ammar, File)
“We routinely will see core temperatures greater than 104, 105 degrees during some of the heat episodes,” Gandhi said. Another degree or three and such a patient is at high risk of death, he said.
How heat kills
Heat kills in three main ways, Jay said. The usual first suspect is heatstroke — critical increases in body temperature that cause organs to fail.
When inner body temperature gets too hot, the body redirects blood flow toward the skin to cool down, Jay said. But that diverts blood and oxygen away from the stomach and intestines, and can allow toxins normally confined to the gut area to leak into circulation.
“That sets off a cascade of effects,” Jay said. “Clotting around the body and multiple organ failure and, ultimately, death.”
But the bigger killer in heat is the strain on the heart, especially for people who have cardiovascular disease, Jay said.
It again starts with blood rushing to the skin to help shed core heat. That causes blood pressure to drop. The heart responds by trying to pump more blood to keep you from passing out.
“You’re asking the heart to do a lot more work than it usually has to do,” Jay said. For someone with a heart condition “it’s like running for a bus with dodgy (hamstring). Something’s going to give.”
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The third main way is dangerous dehydration. As people sweat, they lose liquids to a point that can severely stress kidneys, Jay said.
Many people may not realize their danger, Houston’s Gandhi said.
Dehydration can progress into shock, causing organs to shut down from lack of blood, oxygen and nutrients, leading to seizures and death, said Dr. Renee Salas, a Harvard University professor of public health and an emergency room physician at Massachusetts General Hospital.
“Dehydration can be very dangerous and even deadly for everyone if it gets bad enough — but it is especially dangerous for those with medical conditions and on certain medications,” Salas said.
Dehydration also reduces blood flow and magnifies cardiac problems, Jay said.
Intense heat can ‘fry’ your brain
Heat also affects the brain. It can cause a person to have confusion, or trouble thinking, several doctors said.
“One of the first symptoms you’re getting into trouble with the heat is if you get confused,” said University of Washington public health and climate professor Kris Ebi. That’s little help as a symptom because the person suffering from the heat is unlikely to recognize it, she said. And it becomes a bigger problem as people age.
One of the classic definitions of heat stroke is a core body temperature of 104 degrees “coupled with cognitive dysfunction,” said Pennsylvania State University physiology professor W. Larry Kenney.
Heat and humidity are a dangerous duo
Some scientists use a complicated outside temperature measurement called wet bulb globe temperature, which takes into account humidity, solar radiation and wind. In the past, it was thought that a wet-bulb reading of 95 Fahrenheit was the point when the body started having trouble, said Kenney, who also runs a hot box lab and has done nearly 600 tests with volunteers.
His tests show the wet-bulb danger point is closer to 87. That’s a figure that has started to appear in the Middle East, he said.
And that’s just for young healthy people. For older people, the danger point is a wet bulb temperature of 82, he said.
“Humid heat waves kill a lot more people than dry heat waves,” Kenney said.
When Kenney tested young and old people in dry heat, young volunteers could function until 125.6 degrees, while the elderly had to stop at 109.4. With high or moderate humidity, the people could not function at nearly as high a temperature, he said.
“Humidity impacts the ability of sweat to evaporate,” Jay said.
How to cool down heat exhaustion patients
Heatstroke is an emergency, and medical workers try to cool a victim down within 30 minutes, Salas said.
The best way: Cold water immersion. Basically, “you drop them in a water bucket,” Salas said.
But those aren’t always around. So emergency rooms pump patients with cool fluids intravenously, spray them with misters, put ice packs in armpits and groins and place them on a chilling mat with cold water running inside it.
Sometimes it doesn’t work.
“We call it the silent killer because it’s not this kind of visually dramatic event,” Jay said. “It’s insidious. It’s hidden.”
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A highly contagious digestive virus is surging across the U.S., experts warn.
Rotavirus, a double-stranded RNA virus, causes acute gastroenteritis — inflammation of the stomach and intestines — which can lead to severe diarrhea, vomiting, fever and stomach pain.
The virus primarily affects infants and young children, but there have also been outbreaks in elderly populations, such as nursing homes.
AT LEAST 46 CHILDREN DEAD AMID MEASLES OUTBREAK AS VIRUS SPREADS GLOBALLY
Data from the Centers for Disease Control and Prevention shows that in the week ending April 4, out of 2,329 rotavirus tests, 7.3% were positive for the infection. Last year’s highest infection rate was 6.77% as of the week ending April 19.
Rotavirus, a double-stranded RNA virus, causes acute gastroenteritis — inflammation of the stomach and intestines — which can lead to severe diarrhea, vomiting, fever and stomach pain. (iStock)
“We’re seeing a lot of rotavirus in the wastewater right now,” Dr. Marc Siegel, Fox News senior medical analyst, confirmed to Fox News Digital. “Testing for rotavirus is way down, but the percentage of positive tests is up.”
While the virus typically peaks in the spring, it is not currently slowing down, he noted.
Why cases may be rising
Patricia Pinto-Garcia, M.D., a medical editor at GoodRx who is based in California, said there are several possible reasons for the rotavirus spike.
“Vaccine rates are down overall among young children, as they decreased during COVID,” she told Fox News Digital. “This means there’s a growing number of infants and young children who are vulnerable to infection.”
The rotavirus vaccine series must be completed by the time a child is 8 months old, she noted.
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As a result of the declining vaccinations, herd immunity isn’t protecting vulnerable children, according to Pinto-Garcia. “Children who haven’t finished the vaccine series yet, are too young to get vaccinated, or can’t get the vaccine due to medical illness are more likely to get exposed to the illness because other children aren’t vaccinated,” she said.
Siegel noted that before the vaccine became available, rotavirus resulted in 55,000 to 70,000 in the U.S. per year.
“Vaccine rates are down overall among young children, as they decreased during COVID,” a doctor told Fox News Digital. “This means there’s a growing number of infants and young children who are vulnerable to infection.” (iStock)
“I am concerned that the vaccination rate has been declining over the past seven years and is continuing to decline in the current climate of vaccine skepticism,” he said.
Surveillance methods are also much better than they used to be, Pinto-Garcia noted, which means public health experts are able to pick up and track cases better than ever before.
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“But we see that rotavirus-related healthcare visits are also up, so improved detection is not the only reason we are seeing this spike,” she said.
The COVID pandemic also disrupted the pattern of infections, according to Pinto-Garcia, so it’s “tricky” to compare the current levels against older cycles.
“It’s possible that what we are seeing is still some post-pandemic rebound, but it’s unlikely that this year’s pattern is fully explained by just this factor,” she added.
Transmission and risk
Dr. Zachary Hoy, a pediatric infectious disease specialist at Pediatrix Medical Group based in Nashville, Tennessee, often sees young patients with rotavirus.
“Rotavirus is spread via the fecal-oral route, meaning that a person comes into contact with virus droplets from contact with other children or adults, or from contact with objects such as toys that have been contaminated with the virus from someone who is sick,” he told Fox News Digital. “This can lead to outbreaks, especially at schools where many young children share the same toys.”
“It’s possible that what we are seeing is still some post-pandemic rebound, but it’s unlikely that this year’s pattern is fully explained by just this factor.”
Rotavirus is associated with many dehydration cases in the hospital due to the degree of diarrhea, according to Hoy.
In some severe cases, the virus can lead to seizures due to electrolyte imbalances from dehydration and loss of electrolytes in the stool.
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“Younger children do not have the reserves that older children and adults have, so they can become more dehydrated quicker and develop more severe electrolyte imbalances, leading to more severe infections,” Hoy said.
“Patients with problems with their immune systems or on medications that can decrease their immune systems can have more severe and prolonged infections, too.”
Treatment and care
Because rotavirus is a viral infection, antibiotics are not effective against it. There is no specific antiviral treatment for the condition, with doctors typically recommending supportive care.
“The mainstay of treatment is hospitalization for rehydration via intravenous (IV) fluids,” Hoy told Fox News Digital. “Sometimes it can take up to two to three days of IV fluids to help get patients rehydrated.”
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Blood draws are often necessary to evaluate patients’ electrolyte levels, such as sodium, potassium, calcium and magnesium, according to the doctor.
“If these electrolyte levels are significantly low, sometimes patients need special IV solutions or individual electrolyte medications,” he added.
“The mainstay of treatment is hospitalization for rehydration via intravenous (IV) fluids,” a doctor told Fox News Digital. (iStock)
Dr. Daniel Park, medical director of the Pediatric Emergency Department at UNC Health in Chapel Hill, North Carolina, noted that most children recover with supportive care, but parents should seek medical attention if a child shows signs of dehydration. Those include decreased urination, lethargy or inability to keep fluids down.
“While rare, rotavirus can be life-threatening in vulnerable populations, especially very young infants or children with underlying medical conditions,” Park told Fox News Digital.
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Prevention strategies
Given the lack of antiviral medications for rotavirus, doctors emphasize the importance of prevention, primarily the vaccine.
There are two rotavirus vaccines – Rotateq (a three-dose series) and Rotarix (a two-dose series). They are given starting at age 2 months as oral drops, not injections, according to Hoy.
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“It’s important to get the rotavirus vaccines on schedule, because these younger infants are at greatest risk if they get rotavirus,” he advised.
Other recommended prevention methods include handwashing with soap and water.
Every day we’re faced with a zillion small choices: Go to sleep early, or watch one more episode of that Netflix drama. Call an old friend to catch up, or cruise social media. Of course, no single action will guarantee a long, healthy life or doom you to an early grave. But those little daily decisions do add up, and over the long term they can make a difference when it comes to both your longevity and your health span, the amount of life spent in relatively good health.
Scroll through this theoretical “day in the life” and select the option that best fits your typical day. Not every situation will apply perfectly, but think about which choice you’d be most likely to make. This isn’t a formal scientific assessment. The goal here isn’t to assign you a “good” or “bad” score, but to help you understand the central factors that shape the way we age and how long we live.
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A study from Harvard Medical School indicates natural selection has favored the red hair gene, resulting in a potential increase in the number of redheaded people as humanity continues to evolve.
By analyzing nearly 16,000 ancient genomes spanning 10,000 years, researchers identified a list of traits that nature is actively pushing forward. Among the most prominent were the genetic variants for red hair.
“Perhaps having red hair was beneficial 4,000 years ago, or perhaps it came along for the ride with a more important trait,” the authors noted.
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The study, published in the journal Nature, relied on a large database of ancient DNA from West Eurasia. Using new computing methods, the team was able to filter out random fluctuations in DNA to identify what it called “directional selection.”
Directional selection happens when a particular version of a gene gives an organism a strong survival or reproductive advantage, causing it to become more common in a population faster than it would by chance, according to experts.
Directional selection is when a specific gene provides such significant benefits that it rises in frequency across a population much faster than random chance. (iStock)
Prior to this study, scientists only knew of about 21 such instances in human history, one of which was lactose tolerance. This new research uncovered hundreds more.
“With these new techniques and a large amount of ancient genomic data, we can now watch how selection shaped biology in real time,” Ali Akbari, first author of the study and senior staff scientist in the lab of Harvard geneticist David Reich, said in a press release.
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The data showed that genetic markers for red hair are among 479 gene variants that have been strongly favored over the past 10,000 years. One likely explanation, the researchers said, is a major shift in human history: the transition to farming.
Scientists have long pointed to vitamin D synthesis as a likely driver for the rise of traits like fair skin and light hair. (iStock)
As humans moved away from hunting and gathering and settled into agricultural societies, their environment and behavior changed radically, triggering an evolutionary “acceleration.”
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While the Harvard study provides the first definitive statistical proof that red hair was actively selected during the rise of farming, the researchers noted that the exact prehistoric benefit still requires more study.
However, scientists have long pointed to vitamin D synthesis as a likely driver for the rise of these light-pigmented traits in northern climates.
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While redheads remain a minority of the global population today, the Harvard study’s analysis suggests that they may not be an evolutionary accident.
While redheads remain a minority of the global population today, the Harvard study’s analysis suggests they may not be an evolutionary accident. (iStock)
Instead, the red hair trait was “boosted” by natural selection as humans adapted to the challenges of a modern world, according to the researchers.
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The researchers urged caution in how these findings are interpreted.
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“What a variant is associated with now is not necessarily why an allele propagated,” the authors noted.
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