The number of measles cases associated with an outbreak in western Texas has grown to 309, with 30 cases reported over the last three days, according to new data released Friday.

This means the total number of Texas cases linked to the outbreak in roughly two months has surpassed 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.

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

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

Children and teenagers between ages 5 and 17 make up the majority of cases, at 130, followed by children ages 4 and under accounting for 102 cases.

There have been two U.S. deaths linked to measles this year, with one confirmed and one under investigation.

The confirmed death was an unvaccinated school-aged child in Texas. The child did not have any known underlying conditions, according to DSHS.

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 42 measles cases so far this year, according to the NMDOH. Many of the cases have been confirmed in Lea County, which borders western Texas. Four of the New Mexico cases occurred in people who were vaccinated with at least one MMR dose, while 30 cases were reported in unvaccinated individuals, according to the NMDOH. Eight of the cases presented in people whose vaccination status is unknown.

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

The CDC has confirmed 301 measles cases in at least 14 states so far this year as of last week, including Alaska, California, Florida, Georgia, Kentucky, Maryland, New Jersey, New Mexico, New York, 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 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 recommends that people receive two doses of the MMR vaccine, the first at ages 12 to 15 months and the second dose between 4 and 6 years of age.

One dose is 93% effective and two doses are 97% effective in preventing measles, the CDC says. Most vaccinated adults don’t need a booster, per the health agency.

In the face of the growing measles outbreak, the CDC issued an alert on March 7, saying that parents in the outbreak area should consider getting their children their first MMR vaccine between ages 6 and 11 months, followed by the previously recommended scheduled doses at 12-15 months and then at 4-6 years old, for a total of three vaccinations. 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.