A measles case diagnosed in San Antonio last week originated with an adult foreign traveler who was visiting the area, state health officials said Wednesday.

The case marks the first confirmed instance of measles in Bexar County for more than a decade. The infected person was visiting Guadalupe County from the Philippines, where there is an active outbreak of the highly contagious virus, according to the Texas Department of State Health Services.

State officials do not believe the individual visited public areas in Guadalupe County while infectious. An investigation is ongoing and will include the person’s movements in San Antonio as well, said Chris Van Deusen, spokesman for DSHS. According to University Health System, the diagnosis was made in one of its laboratories after the person was treated as an outpatient sometime last week.

Related: First measles case diagnosed in San Antonio

Until then, the San Antonio area had not officially identified a person with measles since 2007, when three people in the county were found to be infected, according to state data.

Although the person was diagnosed in San Antonio, infectious cases like measles are investigated based on where the person resides or is staying, as opposed to where they are treated. The case is being handled by DSHS Public Health Region 8, which encompasses 28 counties in South and Central Texas. Most of those counties, including Guadalupe, lack their own local health departments.

The latest patient brought the total number of measles cases diagnosed in Texas so far this year to 10, including another case recently confirmed in Jefferson County. The majority are in the Houston area, including four in Harris County and one each in Montgomery and Galveston counties. Cases have also been identified in Bell and Denton counties.

In the first three months of 2019, the state has already outpaced the total number of measles cases confirmed during the course of 2018, when it reported nine cases. There was one case in Texas in 2017.

On ExpressNews.com: Lack of vaccinations linked to measles outbreak

Unlike previous measles outbreaks, Van Deusen said the cases in Texas this year do not appear to be connected to anti-vaccination sentiment and appear unrelated to each other. Nonetheless, he said, the state is monitoring for outbreaks that begin to “perpetuate” themselves.

“Where we get the most concern where if we see some sort of sustained transmission within Texas. You see multiple generations being infected within the state,” Van Deusen said. “It spreads very easily in a community. It’s just a reminder for people to protect themselves, and the simplest way to do that is the measles vaccine.”

A diagnosis of measles in the San Antonio area comes as 11 states, including Texas, grapple with outbreaks or isolated reports of the virus, which can be prevented by the two-dose MMR vaccine, which protects against measles, mumps and rubella. The vaccine is about 97 percent effective if both doses are administered and 93 percent effective after the first dose, according to the Centers for Disease Control and Prevention.

A small percentage of people who get the measles vaccine still are not protected, said Cherise Rohr-Allegrini, San Antonio program director for the Immunization Partnership, a Houston-based nonprofit that seeks to eliminate vaccine-preventable diseases across the state. The vaccine does not work for some people, she said, leaving them vulnerable to the disease.

Such individuals, as well as unvaccinated people, those who cannot get the vaccine for medical reasons and children under the age of 1, are all susceptible to measles. Infants, who cannot receive the first dose until they are 12 to 15 months old, are more likely to suffer serious and sometimes fatal complications.

Rohr-Allegrini said “it was a matter of time” before a major metropolitan area like San Antonio saw a confirmed case of measles, considering its presence in other areas of the state this year.

While the public may not consider one case on its own “that big a deal,” she said, “it’s a huge deal for a disease that should have been eradicated by now, because we have such an effective vaccine.”

Lauren Caruba covers health care and medicine in the San Antonio and Bexar County area. Read her on our free site, mySA.com, and on our subscriber site, ExpressNews.com. | lcaruba@express-news.net | Twitter: @LaurenCaruba