Millions sweltering under extreme heat worldwide as summer arrives Deadly heatwaves are scorching cities on four continents as the Northern Hemisphere marks the first day of summer, a sign that climate change may again help to fuel record-breaking heat that could surpass last summer as the warmest in 2,000 years. Gloria Dickie Reuters

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What’s Really Going on With Bird Flu Wastewater Data

Wastewater, which can measure how much virus humans excrete, has become a valuable disease-tracking tool.

But using that tool to track our current viral threat, the H5N1 bird flu that has begun circulating in cows, is much trickier. Finding even high levels of bird flu in wastewater does not necessarily mean an area is experiencing an outbreak. Rather, it sets off a hunt for the source.