© SAEED KHAN/AFP via Getty Images A man cools down in front of a mist fan for relief from the hot weather in Melbourne, Australia.

Rising temperatures triggering extreme weather events around the world could result in an increase in heat-related illnesses and deaths, as well as the threat of new infectious diseases, according to experts.

We just wrapped the planet's second-hottest year and the hottest decade in recorded history.

Scientists predict that future summers will "smash" temperature records, with developing countries and small islands facing the greatest threat.

Now a new paper published in the Journal of Clinical Investigation, says that with climate change, we can expect cases of heat cramps, heat exhaustion, and potentially fatal heat strokes to climb.

How climate change affects our body temperature

Our bodies have the ability to regulate themselves within a few degrees of the ideal core body temperature of 98.6°Fahrenheit. Body temperature is influenced by the environment, homeostasis (internal mechanisms that maintain our bodies stability in order to survive), and the things we do to adapt to the external or outside temperature, like putting on a jacket when we feel cold or turning on the air conditioner when we feel warm.

© Scott Olson/Getty Images Children cool off in downtown Chicago during heat wave in July 2019.

Johns Hopkins University School of Medicine Professor Rexford Ahima said hotter temperatures will make heat waves "more frequent and intense."

Extreme heat will particularly impact children, older people, people who suffer from chronic conditions and those who live in underserved communities.

This surge will impact tropical and sub-tropical regions the most, according to Ahima.

Extreme heat was felt across the world last year.

Record-setting and deadly heat waves swept Europe. In the United States, a heat wave threatened about 157 million Americans in July. That same month, temperatures in Alaska climbed to 90 degrees, an all-time high. Australia experienced record-breaking temperatures in December as historic fires continue burning across New South Wales state.

"Extreme heat spurred by global warming poses an existential threat to human populations," Ahima wrote in the medical journal, adding that solutions should include "short-term strategies to adapt to the current temperatures, as well as long-term strategies to drastically reduce future emissions of greenhouse gases."

New diseases could stem from warming temperatures

Higher temperatures could also lead to a new crop of infectious diseases, according to a new paper by Arturo Casadevall, a professor at Johns Hopkins University School of Medicine.

That's because microbes, Casadevall said, have the ability to adapt to warmer temperatures.

Microbes live in water, soil, air, and in the human body too. Some microbes can make us sick. The most common types are bacteria, viruses, and fungi.

Our immune system protects us from infectious diseases, including our ability to maintain a stable body temperature. One of these defenses is known as endothermy, which keeps our bodies warm, protecting us from potentially harmful microbes. One example is when we come down with a fever because of an infection: our bodies are working to kill the virus or bacteria that caused the infection.

But Casadevall argued that some fungi species can adapt to higher temperatures, and those that can produce diseases on humans "will break through" the defenses our immune system provides us.

Casadevall said that a large number of fungal species are known to have defeated the immunity of plants and cold-blooded animals.

"If [fungi] can adapt to higher temperatures, that could pose a new threat to humans," Casadevall said.

Casadevall added the same logic can be applied to viruses, bacteria, and parasites.

"If these threats materialize, medicine will need to confront new infectious diseases for which it has no experience," Casadevall said.

The World Health Organization this month listed both climate change, infectious diseases and antimicrobial resistance among the health challenges we're facing the next decade.

WHO, the United Nations' public health agency, noted that climate change has been linked with the spread of infectious diseases such as malaria.