As temperatures around the world rise because of climate change, the human body is increasingly confronting a little-understood and increasing hazard: excessive heat. From enduring heatwaves to sweltering heat waves with high humidity, what used to be a seasonal annoyance is now a worldwide health risk. But how hot is too hot for the human body? At what point does heat become deadly—and why?

In 2020, an article published in Science Advances identified a precise threshold by which the human body cannot survive: 95°F (35°C) wet-bulb temperature. Unlike regular temperature readings, wet-bulb temperature takes into consideration both heat and humidity. It is measured with a thermometer covered in a cloth soaked in water, replicating the way the human body dissipates heat—by evaporating sweat.

If the air surrounding the body is too moist, sweat does not evaporate. When this system breaks down, so does the body's control over internal temperature. The result? A speedy and potentially dangerous increase in core temperature.

In perspective, 115°F (46.1°C) air temperature with 30% humidity yields a wet-bulb temperature of approximately 87°F (30.5°C)—still survivable. However, a seemingly "cooler" 102°F (38.9°C) day with 77% humidity brings the wet-bulb temperature to the lethal 95°F (35°C) mark.

Once wet-bulb temperatures reach this tipping point, sweat can no longer evaporate fast enough to cool the body. Even if the skin is wet, the internal temperature continues to climb. At this stage, hyperthermia sets in—defined by a body temperature above 104°F (40°C)—leading to symptoms like confusion, rapid heart rate, organ failure, and even death.

Who’s Most at Risk?

Although no human can live above a wet-bulb temperature of 95°F, not all people are equally at risk in lower heat exposures.

• Older people, because of impaired thermoregulation.
• Obese or chronically ill people, such as those with cardiovascular disease.
• Those on certain medications, e.g., antipsychotics or beta-blockers.
• Workers outdoors and athletes, whose exertion increases body heat.

Even healthy individuals can succumb to lower wet-bulb temperatures if they are exerting themselves in direct sun or in poorly ventilated environments.

What Happens Inside the Body During Heat Exposure?

The human body contains approximately 60% water, and fluid balance is inextricably linked with temperature regulation. In hot temperatures, the body loses water quickly through sweat and respiration. If it is not replaced, dehydration occurs, causing blood volume to decrease. This affects anything from organ function to delivery of oxygen at the cellular level.

Meanwhile, the thermoregulatory system, which depends on blood flow to shuttle heat from internal organs out to the skin, starts to fail. If this cooling circuit fails, internal organs become overheated, cells start dying, and a chain of failure results in heat stroke or cardiovascular collapse.

How Hot Is Too Hot, Really?

Whereas wet-bulb temperature gives us one measurement, research indicates the ambient air temperature limit of human survival is probably between 104°F and 122°F (40°C–50°C). 122°F is at the limits of what the body can withstand while keeping its core temperature stable, says a 2021 Physiology Report.

A different approach to research implies that the temperature at which the body begins to sweat is 89.6°F (32°C)—the beginning of heat strain. Thus, danger doesn't begin at extreme temperatures only; it accumulates with time, particularly due to long exposure and high humidity.

The U.S. Environmental Protection Agency (EPA) has documented that heat directly caused 11,000 fatalities in the United States between 1979 and 2018, although the actual number is probably much greater because underreporting is likely to have occurred. While hurricanes or flooding may be dramatic, they kill openly, but heat waves are deadly killers that silently take victims in poor communities, older people, and those not having air conditioning.

Moreover, heat exacerbates existing conditions, increasing the possibility of strokes, heart attacks, and breathing difficulties during heat waves.

How to Survive Extreme Heat?

We may not be able to manipulate the weather, but we can manage our environment and lifestyle. Experts advise:

• Rehydrate with electrolytes, not plain water. Sweating excessively loses salt and minerals necessary for cellular processes.
• Lower internal body temperature by bathing or showering with cool water.
• Avoid sun exposure, particularly between 10 AM and 4 PM.
• Dress in light, loose clothing and have lighter, more frequent meals.

Use extra caution with electric fans during high heat; they can accelerate evaporation and boost dehydration.

In addition, the Centers for Disease Control and Prevention (CDC) recommends visiting during heatwaves susceptible populations—i.e., people who are frail or have disability and ensuring air conditioning, shades, or available cooling resources like fans or air conditioning are at their disposal.

The highest temperature that a human can tolerate is not one number—it's a function of heat, humidity, and time. Wet-bulb temperatures over 95°F are universally lethal within a few hours, but even lower temperatures can be severely dangerous under the right conditions. As climate change accelerates, our knowledge of and readiness for extreme heat must keep pace. This isn't merely a meteorological issue—it's a public health emergency in the making.

New Delhi: Meningitis may not have been the talk of the town, but it is now making headlines after an outbreak in the UK wreaked havoc on students—the outbreak recently resulted in the death of two students, and 11 others have been hospitalised. The outbreak is being linked to a nightclub event in Canterbury, Kent. Following this, the UK Health Security Agency contacted 30,000 students, staff, and their family members, along with anyone who visited the club from March 5 to March 7. This was a precautionary measure, they said, and a new report by UK health officials suggests that meningitis B has caused the outbreak. But what is most shocking is how this infection makes its way into your body.

What is meningitis?

Meningitis is an infection of the protective membranes around the spinal cord and the brain. It can become very serious if not treated or diagnosed in time. It is a consequence of bacterial or viral infection. Despite being a rare occurrence, the infection can spread through coughs, sneezes, a cold, or physical contact in the form of kissing.

Uncommon ways of contracting meningitis

Some of your daily habits may seem normal, but in turn, they can be among the worst ways to catch meningitis. Some of the most obscure ways are:

Vaping: Reminder—vaping might be common now, but that does not make it a safe practice. It is associated with respiratory disorders and even lung collapse in some cases. When it comes to meningitis, vaping can be a means of passing germs on to another person—for instance, by sharing a contaminated vape. The meningococcus bacteria can harmlessly live in the throat without showing any symptoms, but in order to cause damage, it must cross the nasopharyngeal barrier.

Second-hand smoke: Second-hand smoke may not just cause cancer, but also meningitis. This risk is particularly prevalent in children, as it may increase their chances of developing invasive meningococcal disease, a serious form of meningitis. Experts from the University of Nottingham have noted that breathing in smoke from someone else's cigarette can make one more vulnerable to infection. This makes people more likely to harbour meningitis-related bacteria in the throat and nose, thus leading to infection.

Worm infection: Some types of parasites, such as tapeworms, can cause a rare type of meningitis known as eosinophilic meningitis. These worms take residence in the gut and feed on nutrients that the body needs to stay healthy. This can result in diarrhoea, nausea, and tiredness. If the infection spreads to the brain, it can cause meningitis. Despite being rare, it is still a possibility.

Sharing cutlery: Meningitis can spread through close contact, and sharing cutlery can be one of the most overlooked ways. This can also include sharing toothbrushes. The infection can spread through droplets and saliva.

Unwashed hands: An act of laziness can cost you in the long run; therefore, using a sanitiser or regularly washing hands is a must. Experts say that particles from faeces can linger on the hands, and ingesting them in any way can lead to infections such as meningitis. The infection can also spread through coughing and sneezing.

A team of US researchers has developed a novel nasal swab test, akin to those used to detect COVID-19 infections, which can spot early signs of Alzheimer's Disease -- affecting over 55 million people worldwide.

The condition is treatable in early stages to manage symptoms and slow cognitive decline. However, it remains the hardest to detect, affecting treatment outcomes. The brain changes can begin 10 to 20 years before symptoms become apparent.

The novel outpatient nasal swab, developed by Duke University researchers, has shown promise in picking up early biological changes linked to Alzheimer's. It can spot the degenerative condition, even before problems related to thinking and memory begin to appear.

"We want to be able to confirm Alzheimer's very early, before damage has a chance to build up in the brain," said Bradley J. Goldstein, professor at Duke University's School of Medicine.

"If we can diagnose people early enough, we might be able to start therapies that prevent them from ever developing clinical Alzheimer's," Goldstein added.

How Effective Was The Nasal Swab?

In the study, published in the journal Nature Communications, the team placed a gentle swab high inside the nose of 22 participants.

The swab collected thousands of nerve and immune cells to see which genes are active.

The analysis clearly differentiated people with early or diagnosed Alzheimer's from those without the disease -- 81 percent of the time. It also included people with no symptoms.

Alzheimer’s Disease: The Leading Cause of Dementia

Alzheimer's disease is one of the most common forms of dementia and mostly affects adults over the age of 65.

About 8.8 million Indians aged 60 and above are estimated to be living with Alzheimer's disease. Over seven million people in the US, 65 and older, live with the condition, and over 100,00 die from it annually.

Alzheimer's disease is believed to be caused by the development of toxic amyloid and beta proteins in the brain, which can accumulate and damage cells responsible for memory.

While there is no clear cause of Alzheimer's disease, experts believe it can develop due to genetic mutations and lifestyle choices, such as physical inactivity

unhealthy diet

social isolation.

Early symptoms of Alzheimer's disease include forgetting recent events or conversations. Other signs include:

• losing or misplacing things
• getting lost when walking or driving
• being confused, even in familiar places
• losing track of time
• difficulties solving problems or making decisions
• difficulties performing familiar tasks
• misjudging distances to objects visually.

Over time, Alzheimer's disease leads to serious memory loss and affects a person's ability to do everyday tasks.

Currently, there is no cure for this progressive brain disorder, and in advanced stages, loss of brain function can cause dehydration, poor nutrition, or infection. These complications can result in death.

Being physically active and taking part in activities and social interactions that stimulate the brain and maintain daily function can help prevent the condition.

The Human papillomavirus (HPV) vaccine is one of the most important advances in preventive healthcare, with the unique ability to prevent cancers.

Evidence consistently shows that the most appropriate age for HPV vaccination is between 9 and 14 years. At this stage, children develop a significantly stronger immune response, producing higher antibody titers than older adolescents and adults.

This enhanced immunogenicity translates into durable and highly effective protection and also allows simplified schedules, including the possibility of single-dose protection, thereby improving feasibility and coverage at a population level.

HPV Vaccine: Why Age 14 Matters The Most

The emphasis on vaccination by the age of 14 years is particularly important. Beyond this age, the immune response is relatively lower, and the number of doses required increases, making early vaccination both scientifically and programmatically more efficient.

Recognizing this, the Government of India has adopted a strategy of administering a single-dose HPV vaccine to adolescents up to 14 years of age through school- and community-based outreach programs. The program utilizes the Gardasil vaccine, which has an established track record of safety and efficacy over nearly two decades.

Equally critical is the timing of vaccination in relation to exposure. HPV is primarily transmitted through sexual contact, and vaccination before exposure ensures maximum effectiveness. Administering the vaccine in early adolescence provides protection well before any potential risk, making it a true preventive intervention with near-complete benefit.

Persistent infection with high-risk HPV types is a well-established cause of several cancers. In India, cervical cancer continues to be one of the leading causes of cancer-related illness and death among women. While HPV is also responsible for anal, penile, and oropharyngeal cancers, the burden of cervical cancer is substantially higher, which has historically led to a greater focus on vaccinating girls.

HPV: Are Boys At Risk?

However, HPV infection affects both genders. Boys are also at risk of HPV-related diseases, including anal and penile cancers, genital warts, and oropharyngeal cancers, the incidence of which is rising globally.

Vaccinating boys offers direct protection to them and also contributes to reducing transmission within the community. A broader, gender-inclusive approach has the potential to enhance population-level protection.

Public health agencies, including the World Health Organization, have emphasized HPV vaccination as a key strategy in cancer prevention and in reducing the long-term burden of non-communicable diseases.

HPV Vaccine: Part of Adolescent Health Check-ups

Integrating HPV vaccination into routine adolescent health check-ups can further normalize it as a standard preventive health measure. This approach can complement government efforts by encouraging participation from the private healthcare sector and improving overall uptake.

HPV vaccination in the 9–14 year age group is therefore not merely a recommendation; it is a time-sensitive, evidence-based intervention that can prevent cancers decades later. Strengthening awareness and ensuring timely vaccination will be critical in reducing the future burden of HPV-related cancers in India.