Over 100 new measles cases have been confirmed in South Carolina since Jan. 9, state officials said Tuesday.

The South Carolina Department of Public Health (DPH) in recent days reported 124 new cases in the state, an expansion of the largest current measles outbreak in the United States.

More than 400 people are in quarantine due to exposure to measles, and another 17 are in isolation, having been found to be infected and contagious, according to the health department.

Measles is a contagious disease that spreads primarily when droplets left by infected people are inhaled.

State officials are encouraging people to receive the measles, mumps, rubella (MMR) vaccine, a 3-in-1 shot. They also say that anyone who was at the South Carolina State Museum from 1 to 5 p.m. on Jan. 2 should watch for symptoms, which usually appear from 7 to 14 days following exposure.

Symptoms for measles include cough, runny nose, red watery eyes, and fever followed by a rash two to three days later that starts on the face before spreading to the rest of the body.

The South Carolina outbreak started in 2025, and the total number of cases linked to it is 434.

Most of the patients have not received a vaccine, although a subset have, according to the South Carolina Department of Health.

A larger outbreak occurred in Texas, but officials over the summer said the outbreak was over.

At least two other states have recently reported cases related to the South Carolina outbreak.

Officials in Washington state said on Jan. 8 that an adult and two children from the same family traveled to the state from South Carolina and were infectious while visiting King and Snohomish counties from Dec. 27, 2025, through Jan. 1, 2026.

The family visited locations including the Seattle-Tacoma International Airport while contagious, but before being diagnosed, the Snohomish County Health Department and Public Health–Seattle & King County said in a statement.

The North Carolina Department of Health and Human Services said in a Jan. 6 statement that three siblings who had visited South Carolina became sick about one to two weeks later.

Two other cases have been confirmed in the state since late December, officials said.

This week, officials in Georgia, Oregon, and Virginia reported cases apparently unrelated to the South Carolina outbreak, potentially stemming from separate exposures or other sources.

Measles was also detected in wastewater in San Bernardino County, California, and Utah County, Utah, during the week ending Jan. 3, according to the Centers for Disease Control and Prevention. Measles was also recently detected in wastewater in Washington County, Oregon; Wake County, North Carolina; and Spartanburg County, South Carolina, where the South Carolina outbreak is centered, the CDC said.

When measles is identified in wastewater, the CDC works with health officials to identify whether people in the area have developed measles symptoms.

Separately, Mecklenburg County Public Health in North Carolina said Monday that measles was detected in wastewater there, although no cases have yet been confirmed.

The CDC says 2,144 measles cases were confirmed in 2025 across 45 jurisdictions, the highest case count in the country since 1991.