The measles outbreak in western Texas is continuing to grow with 20 additional cases confirmed, bringing the total to 279 cases, according to new state data published Tuesday.

Almost 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). Just two cases are among fully vaccinated individuals. At least 36 people have been hospitalized so far, the state said.

In the Texas outbreak, children and teenagers between ages 5 and 17 make up the majority of cases, at 120, followed by children ages 4 and under making up 88 cases, the DSHS data shows.

“Due to the highly contagious nature of this disease, additional cases are likely to occur in the outbreak area and the surrounding communities,” the DSHS said in its update.

The number of measles cases in Texas is close to the number confirmed for the entirety of last year in the U.S., which saw 285 cases nationwide, according to data from the Centers for Disease Control and Prevention

Two likely measles deaths have been reported so far in the U.S. this year. The first reported death was in Texas, according to the DSHS. The child did not have any known underlying conditions, according to the department.

The death was the first U.S. measles death recorded in a decade, according to data from the CDC.

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.

New Mexico has reported a total of 33 measles cases so far this year, according to the NMDOH. Many of the cases have been confirmed in Lea County, which borders western Texas.

Health officials suspect there may be a connection between the Texas and New Mexico cases, but a link has not yet been confirmed.

The CDC has confirmed 301 measles cases in at least 14 states so far this year, including Alaska, California, Florida, Georgia, Kentucky, Maryland, New Jersey, New Mexico, New York, Pennsylvania, Rhode Island, Texas, Vermont and Washington, according to new data published Friday.

The majority of nationally confirmed cases 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 (measles, mumps and rubella) inoculation and 2% are among those who received the required two doses, according to the CDC.

The CDC recommends that people receive two doses of the MMR vaccine, the first at ages 12 to 15 months and the second dose between ages 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, per the health agency.

In the face of the growing measles outbreak, the federal health agency issued an alert on March 7 saying parents in the outbreak area should consider getting their children an early third dose of the MMR vaccine. Texas health officials have also recommended early vaccination for infants living in outbreak areas.

ABC News’ Youri Benadjaoud and Sony Salzman contributed to this report.