When the Permafrost Thaws, Old Diseases Awaken: How Global Warming Is Changing the World's Health Picture

In the summer of 2016, an unusually hot spell in Siberia thawed ground that had stayed frozen for decades. Out of the softened soil emerged the carcass of a reindeer that had died of anthrax long ago. The bacteria had survived in the ice. A child touched the animal, fell ill, and a local outbreak followed. A disease most of us associate with history books and bioweapons had been brought back not by people, but by a warming planet. As PBS NewsHour reported in its coverage of the study, this case is just one of more than a thousand documented links between climate hazards and human illness.

It can feel distant, until it happens to someone you know. Canadian singer Avril Lavigne learned this the hard way. After what she believes was a tick bite in spring, she spent months feeling exhausted, feverish and unable to eat, and saw doctor after doctor before finally being diagnosed with Lyme disease. She told People magazine, as reported by Rolling Stone, that she was bedridden for five months and had no idea a small bug bite could do this. Ticks that carry Lyme disease are now being found in regions that were once too cold for them, and many readers tell us the same story: they never used to check for ticks after a walk, and now it has become a family routine.

When people talk about climate change, most first think of heat waves, melting glaciers and floods. But a lesser-known, yet no less important effect of global warming is its influence on diseases that pass between people and animals. Research in recent years suggests that climate change is not only an environmental issue but also a real concern for our health.

How Does Climate Change Affect Diseases?

In a large study published in the journal Nature Climate Change in 2022, scientists led by Camilo Mora of the University of Hawaiʻi reviewed tens of thousands of scientific papers on 375 different infectious diseases that affect people around the world. They found that 218 of them (58%) had, at some point, been made worse by climate-related hazards such as heat, heavy rainfall, floods and drought. Altogether they identified 1,006 distinct pathways from a climate hazard to a human illness. The researchers also created an interactive map of these disease pathways that anyone can explore.

These changes happen in different ways. After floods, standing water can boost the number of mosquitoes that carry diseases such as malaria and chikungunya. During droughts, bats and other wild animals may move closer to human settlements in search of food and water, increasing the chance that viruses jump to people. As oceans warm, bacteria of the Vibrio family multiply more easily; one of them, Vibrio cholerae, causes cholera, while others can cause vibriosis after eating raw seafood or swimming in warm coastal water. Heat waves, meanwhile, put extra strain on the body and can leave vulnerable people less able to cope with infections.

These are no longer just theories. They are things that are already happening. Study leader Camilo Mora stressed that the research is not a forecast: in his words, there is no speculation here, these are things that have already happened.

Real-World Examples

The stories from recent years are surprisingly clear. In 2016 in Siberia, higher temperatures thawed permafrost that had been frozen for decades. The carcass of a reindeer infected with anthrax emerged from it. A child who touched the animal became infected, which triggered an outbreak in the region. Anthrax is a disease we usually associate with war and weapons, but here nature itself brought an old illness back to life.

Another example comes from Colombia, and it is personal for the study's lead author. In 2014, Mora's family home was flooded so badly that, for the first time in his memory, there was water inside the living quarters. As NBC News described, the floodwater created ideal breeding conditions for mosquitoes, and he was infected with the chikungunya virus. This illness causes severe joint pain that can resemble rheumatism. Mora recovered, but he says he still feels the consequences in his joints today.

What Do the Numbers Say?

The World Health Organization (WHO) estimates that between 2030 and 2050, climate change could cause around 250,000 additional deaths per year from undernutrition, malaria, diarrhoea and heat stress alone.

Malaria remains one of the clearest warning signs. According to the WHO World Malaria Reports, there were an estimated 241 million malaria cases worldwide in 2020, the vast majority of them in Africa, and the numbers have since remained stubbornly high.

Europe is not untouched either. The European Centre for Disease Prevention and Control (ECDC) has recorded locally acquired chikungunya cases in Italy and France, spread by the tiger mosquito, which has settled in many southern and central European regions as summers have become warmer.

Why Is This Our Problem Too?

You might think these are problems for Africa, South America or Siberia, but unfortunately that is not the case. Changes are happening everywhere, including close to home. The severe floods that hit Central Europe in recent years did not only damage houses and roads; floodwater can carry sewage and bacteria into wells and water supplies, which raises the risk of stomach and intestinal infections, especially among children and older people.

Ticks are also becoming more active. In many parts of Europe, they now appear earlier in spring and stay active later into autumn than they did a few decades ago, and the ECDC reports that tick-borne encephalitis is being found in new areas and at higher altitudes. A longer tick season means more opportunities for Lyme disease and tick-borne encephalitis.

A Look Back in History

Physicians knew more than 2,000 years ago that weather influences disease. Hippocrates, whom we know as the father of medicine, wrote a whole treatise, Airs, Waters, Places, about how seasons, winds and water affect health. At the time, nobody knew about viruses and bacteria, yet people already noticed the link between the environment and illness.

Today we have a huge amount of data that confirms this. The real question is: if we know all this, why are we not acting faster?

Why Are Doctors Warning About Climate Change?

Co-author of the study, Jonathan Patz, director of the Global Health Institute at the University of Wisconsin-Madison, has pointed out that when the climate changes, the risk of infectious diseases changes along with it. Other experts, such as Carlos del Rio of Emory University, argue that climate change should be seen as an illness of the Earth, with its own symptoms, and infectious diseases are one of them.

Del Rio, who was not involved in the research, called the findings terrifying in an interview with the Associated Press, adding that infectious disease specialists must make climate change one of their priorities to prevent what he described as a catastrophe.

How to Protect Yourself at Home, Cheaply and Simply

Even though climate change is a global problem, there are everyday steps you can take to lower your personal risk. As a nutrition-minded approach, think of these as small habits that support your body and reduce exposure, not as cures.

• Clean drinking water: our grandmothers already knew that after floods it is best to boil water before drinking it. Bringing water to a rolling boil for at least one minute kills most bacteria that can cause diarrhoea and other waterborne illnesses. The WHO drinking-water fact sheet explains why safe water is so important after natural disasters.



• Protection against mosquitoes and ticks: plant-based repellents are popular, but their protection is often short. Among natural options, oil of lemon eucalyptus is one of the few ingredients recognised by the CDC and registered by the US Environmental Protection Agency, while citronella tends to wear off quickly and needs frequent reapplication. Light, long-sleeved clothing, emptying standing water around the house, and checking your body for ticks after time outdoors are simple, free habits that make a real difference.



• Supporting the immune system with food: garlic, honey and ginger have been part of folk remedies for centuries. Research on garlic is still limited; a Cochrane review found only small studies suggesting fewer colds, and the Operation Supplement Safety program notes that the evidence for garlic supplements is not conclusive. Still, fresh garlic is a flavourful part of a balanced diet. If you want to get the most out of it, read our article What happens if we put garlic in the refrigerator before we cut it. Honey can soothe a sore throat, but should never be given to babies under one year old.



• Fibre for a healthy gut: a large part of our immune system is linked to the gut, and beneficial gut bacteria depend on fibre from whole grains, legumes, fruit and vegetables. Find out why cutting carbohydrates too drastically can backfire in Why You Should Avoid Diets That Exclude Carbohydrates.



• Enough sleep: good sleep is one of the most underrated foundations of a well-functioning immune system, and heat waves often ruin it. Our article When you sleep too little, your belly grows – and you won't even notice this on the scale explains why rest matters more than most people think.



• Herbal teas: elderflower and linden tea are traditional warming drinks in many European homes, especially during colds. They help you stay hydrated and can be comforting, although they are not a treatment for infections.

These are not substitutes for medicine, but they are inexpensive and accessible habits that may help lower your risk if you find yourself in an environment where infectious diseases spread more easily. If you develop a high fever, severe joint pain, a spreading rash after a tick bite, or ongoing diarrhoea, see a doctor promptly.

Frequently Asked Questions

Can thawing permafrost really release old diseases?

Yes, in rare cases. The 2016 anthrax outbreak in Siberia is the best-documented example. Scientists are also studying ancient microbes in permafrost, but most of them pose no known risk to humans.

Are mosquito-borne diseases now a risk in Europe?

Locally acquired cases of chikungunya and dengue have been recorded in parts of southern Europe. The overall risk remains low, but it is growing as the tiger mosquito spreads north.

Can food protect me from infections?

No single food can prevent infections. A varied diet rich in vegetables, fruit, whole grains and legumes, combined with good sleep, clean water and protection from insects, supports your body's natural defences.

The Earth Is Sick, but Solutions Exist

Global warming is no longer a distant threat but a reality we live in today. The increased spread of infectious diseases is one of the clearest signs that the Earth is changing.

Although we cannot fight climate change alone, we can do a lot to protect ourselves and our loved ones. That means taking care of clean water, protecting ourselves from insects, supporting our resistance with good food, rest and herbs, and backing measures that reduce pollution and the warming of the planet.

The truth is that the health of the Earth is directly connected to our own health. If we protect nature, we also protect ourselves.