news explainers

Measles can erase the immune system's "memory" and cause a rare but fatal health condition. The MMR vaccine prevents these repercussions, evidence shows.

As measles outbreaks in the U.S. continue, here's what to know about how the disease spreads, what its symptoms are, and how to protect yourself and community from the illness.

A man in his early 20s received a transplant of his own sperm-producing stem cells, which had been frozen since his childhood, in an attempt to regain fertility. Doctors are waiting to see if the treatment works.

There have been hundreds of measles cases reported in the U.S. since the beginning of the year. Here's what you need to know about measles immunity.

Nearly 119,000 birds have been culled at a farm in California after a bird flu called H5N9 was detected among the poultry.

DeepSeek's V3 and R1 models took the world by storm this week. Here's why they're such a big deal.

A nasal spray that contains esketamine — a potent derivative of ketamine — can now be taken on its own to treat adults with severe depression, the FDA says. Here's what that means.

The FDA has given marketing authorization to Zyn nicotine pouches. That doesn't necessarily mean they're safe to use, especially for young people, and experts say there's little evidence that they help adults quit smoking.

Fluoride is added to tap water in many countries around the world. But why?

An initially "unknown" illness affecting hundreds in the Democratic Republic of the Congo may be attributable to malaria, malnutrition and a viral infection. But investigations are ongoing.