H5N1, an avian flu virus, has killed tens of thousands of marine mammals, and infiltrated American livestock for the first time. Scientists are working quickly to assess how it is evolving and how much of a risk it poses to humans.

In the age of Ozempic, the “fat activist” Virginia Sole-Smith is inspiring and infuriating her followers.

After he made a fortune selling prescription drugs and providing medical information online, he and his wife became leading breeders of thoroughbred horses.

Homeownership is not the boon to older Americans that it once was.

Novo Nordisk’s factories work nonstop turning out Ozempic and Wegovy, its blockbuster weight-loss drugs, but the Danish company has far bigger ambitions.

Testing for H5N1 infection has been limited, and the outbreak was thought to be confined. But asymptomatic cows in North Carolina may have changed all that.

Among those with substance use disorders who have been referred to child welfare, less than half received medication or counseling.

Mammography can miss tumors in women with dense breasts, so their doctors often include ultrasound or M.R.I. scans. Patients often wind up paying the bill.

As record heat enveloped the nation, the rate of emergency room visits increased compared with the previous five years, a sign of the major health risks of high temperatures.

The change followed a sweeping review by England’s National Health Service that found “remarkably weak” evidence for youth gender treatments.

The company has told countries that it can supply only 18.8 million of the 29.6 million doses it was contracted to deliver this year.

After a drawn-out global controversy over the coronavirus, the W.H.O. has updated its classification of how pathogens spread through the air.