Merced County health officials say measles virus found in wastewater
The Merced County Department of Public Health said Friday that the county has detected the measles virus in local wastewater during a routine check.
The public health department has not confirmed any clinical cases of measles in the county, according to a community alert.
Wastewater surveillance serves as a warning sign that can detect viruses shed in bodily waste, the alert said.
Measles is a contagious viral disease that is spread through the air when an infected person breathes, talks, coughs or sneezes. Common symptoms include coughing, diarrhea, runny nose, high fever, ear and eye infections, and a rash all over the body. Measles can lead to severe health problems, including permanent hearing loss and death.
An infected person can spread the disease up to four days before a rash appears, and up to four days after the rash appears.
Health officials urge people who believe they may have been exposed to the measles virus to isolate and immediately seek medical attention. About 90% of unvaccinated individuals exposed to the virus will become infected, according to the Centers for Disease Control and Prevention.
Measles was declared “eliminated” in the U.S. in 2000, but has reemerged after a decline in vaccination rates since the COVID-19 pandemic.
The CDC recommends children receive the MMR (measles, mumps and rubella) vaccine or MMRV (measles, mumps, rubella, and varicella (chickenpox)) vaccine — both protect against chickenpox — at ages 12 to 15 months and again at 4 to 6 years. It is recommended that older children and adults without documented immunity to the virus receive one or two doses of the MMR vaccine 28 days apart.
The vaccine for measles is highly effective: One dose is 93% effective, and the full two-dose course is 97% effective, health officials say. It takes seven to 14 days to begin to benefit from the vaccine.
This story was originally published June 5, 2026 at 12:48 PM.
