Measles Is Now Showing Up in Wastewater

By Alice Park

Jun 3, 2025

Measles cases in the U.S. have been rare in recent decades, thanks to a strong childhood vaccination program. But a few cases inevitably pop up each year as travelers bring the virus in from other countries and infect unvaccinated people, primarily children.

Those cases are no longer blips. Now that the measles vaccination rate is dropping precipitously across the U.S. – due in part to anti-vaccine sentiments – cases are rising. So far in 2025, 14 outbreaks have been reported in 33 states, according to the U.S. Centers for Disease Control and Prevention (CDC). (By comparison, in 2024, there were just 16 outbreaks reported during the entire year.)

Scientists may now have a new way to catch cases. For the first time, researchers have posted national information on where the measles virus is showing up in wastewater.

Wastewater surveillance is a useful public-health tool because it provides an objective glimpse into where a given virus is causing infections – often before traditional testing methods. For viruses like measles, which infected people shed in urine, feces, or saliva, it can provide a critical heads-up for health officials.

Why wastewater monitoring may be especially useful for measles

Doctors who see patients with measles must report the case to the CDC so the agency can track it and respond to any outbreaks. But it takes time for people to develop symptoms, seek medical care, get tested, and then have their case reported if the test is positive. In addition, the first symptoms of measles are common ones like fever, runny nose, and cough – before the telltale rash appears. Plus, not everyone may get sick enough to know they have measles, so their cases may go unreported. Still others may get sick but not have access to health care and therefore never seek medical help.

Wastewater monitoring bypasses those hurdles and can theoretically catch evidence of the virus much earlier. That could be especially helpful with a highly contagious disease like measles, in which one infected person can quickly spread the virus to as many as 18 others.

This type of tracking for measles is too new to know yet whether it can detect cases in a region before people start testing positive. But wastewater surveillance was able to pick up signs of the Covid-19 virus days or sometimes even weeks before cases began appearing in hospitals and testing labs.

(Adapted from: Measles Is Now Showing Up in Wastewater | TIME)