The number of measles cases associated with an outbreak in western Texas has grown to 146, according to new data released Friday.

Almost all of the cases are in unvaccinated individuals or individuals whose vaccination status is unknown, with 79 unvaccinated and 62 of unknown status. At least 20 people have been hospitalized so far, according to the Texas Department of State Health Services (DSHS).

Just five cases have occurred in people vaccinated with one dose of the measles, mumps, rubella (MMR) vaccine.

Children and teenagers between ages 5 and 17 make up the majority of cases with 70, followed by 46 cases among children ages 4 and under.

So far just one death has been reported in an unvaccinated school-aged child, according to DSHS. It marks the first measles death in the U.S. in a decade, according to data from the Centers for Disease Control and Prevention.

Gaines County is the epicenter of the outbreak, with 98 cases confirmed among residents, according to DSHS. State health data shows the number of vaccine exemptions in the county have grown dramatically.

Roughly 7.5% of kindergarteners in the county had parents or guardians who filed for an exemption for at least one vaccine in 2013. Ten years later, that number rose to more than 17.5% — one of the highest in all of Texas, according to state health data.

The CDC as separately confirmed 93 cases in eight states so far this year in Alaska, California, Georgia, New Jersey, New Mexico, New York, Rhode Island and Texas.

The total, however, is an undercount due to delays in reporting from states to the federal government.

The majority of nationally confirmed cases are in people who are unvaccinated or whose vaccination status is unknown. Of the cases, 4% are among those who received one dose of the measles, mumps, rubella (MMR) shot.

Measles is one of the most contagious diseases known to humans. Just one infected patient can spread measles to up to nine out of 10 susceptible close contacts, according to the CDC.

Health officials have been urging anyone who isn’t vaccinated to receive the MMR vaccine.

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. Most vaccinated adults don’t need a booster.

Measles was declared eliminated from the U.S. in 2000 due to the highly effective vaccination program, according to the CDC. However, CDC data shows vaccination rates have been lagging in recent years.

ABC News’ Youri Benadjaoud contributed to this report.