When Trudy Rosler first got sick after a visit to Vancouver Island in British Columbia, doctors were stumped. Eventually, they discovered that she had a fungus growing in her brain stem — one that was previously only known to exist in the tropics. Researchers say that subtle changes in climate over the last 40 years may be the reason it’s infecting people much farther north. Here in the U.S., the Centers for Disease Control and Prevention is already treating climate change as a serious health threat.

Need to Know’s medical correspondent Emily Senay examines how a warming climate is already affecting our health, from making allergies worse to affecting the spread of infectious diseases and pushing the extremes of killer weather:

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PBS climate desk

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