The measles outbreak in western Texas is continuing to grow with 18 cases confirmed over the last five days, bringing the total to 327 cases, according to new data published Tuesday.

Nearly all of the cases are in unvaccinated individuals or in individuals whose vaccination status is unknown, according to the Texas Department of State Health Services (DSHS). At least 40 people have been hospitalized so far.

Just two cases have occurred in people fully vaccinated with the measles, mumps, rubella (MMR) vaccine, according to the data.

In the Texas outbreak, children and teenagers between ages 5 and 17 make up the majority of cases at 140, followed by children ages 4 and under accounting for 105 cases, according to the data.

“Due to the highly contagious nature of this disease, additional cases are likely to occur in the outbreak area and the surrounding communities. DSHS is working with local health departments to investigate the outbreak,” the department said in a press release.

It comes as another case of measles was confirmed in New Mexico, bringing the total to 43, according to data from the state Department of Health. The majority of cases are in Lea County, which borders Gaines County — the epicenter of the outbreak in Texas.

Additionally, two cases of measles were confirmed in Erie County, Pennsylvania, on Monday. A media release from the Erie County Department of Health said the cases were linked to international travel and there is not a high risk of exposure for the general population.

Two likely measles deaths have been reported so far in the U.S. The first was an unvaccinated school-aged child in Texas, according to the DSHS. The child did not have any known underlying conditions, according to the department.

The Texas death was the first measles death recorded in the U.S. in a decade, according to data from the Centers for Disease Control and Prevention.

A possible second measles death was recorded after an unvaccinated New Mexico resident tested positive for the virus following their death. The New Mexico Department of Health (NMDOH) said the official cause of death is still under investigation.

The CDC has confirmed 378 measles cases this year in at least 17 states: Alaska, California, Florida, Georgia, Kansas, Kentucky, Maryland, Michigan, New Jersey, New Mexico, New York, Ohio, Pennsylvania, Rhode Island, Texas, Vermont and Washington. This is likely an undercount due to delays in states reporting cases to the federal health agency.

The majority of nationally confirmed cases, about 95%, are in people who are unvaccinated or whose vaccination status is unknown, the CDC said. Of those cases, 3% are among those who received just one dose of the MMR inoculation and 2% are among those who received the required two doses, according to the CDC.

The CDC currently recommends that people receive two vaccine doses, the first at ages 12 to 15 months and the second between 4 and 6 years old. One dose is 93% effective, and two doses are 97% effective, the CDC says. Most vaccinated adults don’t need a booster.

For those living in the outbreak area, Texas health officials are recommending that parents consider an early dose of the MMR vaccine for children between 6 months and 11 months, and that adults receive a second MMR dose if they only received one in the past.