Measles cases in Texas and New Mexico rose to 351 on Friday, the health departments of the states said, an increase of 34 infections over the last three days as the U.S. deals with one of the largest measles outbreaks in the past decade.

The number of cases in the two states has already surpassed last year's count of 285 infections, according to data from the CDC.

Cases in Gaines County, Texas, the center of the outbreak, rose to 211 from 191 as of March 18, the Texas Department of State Health Services said. Hospitalizations in the state rose to 40 from 36, the department said.

The Texas health department said it has classified 307 patients as "unvaccinated or unknown", which includes people with no recorded doses of measles vaccine more than 14 days before they started showing symptoms.

In New Mexico, cases rose to 42 from 38 on Tuesday, including two cases in Eddy County and the rest in Lea County, which borders Gaines County.

As of March 18, Oklahoma's health department reported four "probable" cases in unvaccinated individuals who were exposed to the outbreaks in Texas and New Mexico and experienced measles-like symptoms.

The CDC has said the measles, MMR vaccine is the most important tool for preventing measles.

In a health advisory to doctors on March 7, the CDC said that the risk for widespread measles in the U.S. remained low.

U.S. Health Secretary Robert F. Kennedy Jr, who has for years sown doubts about the safety and efficacy of immunization, said last month that he recognizes the serious impact of the current measles outbreak in Texas and said the government is providing resources, including vaccines.