Los Angeles County's public health department said Thursday that it has confirmed an "outbreak" of seven new measles cases over the past month.

While not identifying the individuals, the County Department of Public Health said none were vaccinated against the disease, according to its preliminary investigation.

The department "is classifying this as an outbreak," it said, adding that the first person who got sick developed symptoms in late November. Since then, the agency said, there has been "one wave" of additional cases.

For privacy reasons, Public Health has not revealed the patients' ages or where they were infected, although it noted that "most of the cases" are "epidemiologically linked."

The department said it is monitoring the situation to see if any additional cases occur.

"Some exposures may have occurred in public locations," Public Health said, adding that it's investigating those cases. If the department can identify and contact all people who might have been exposed to the virus, it will not release information about these locations, it said. But the agency says if it can't reach everyone, it will release that information to the public.

While Public Health said there have been sporadic cases in the past 20 months, this is the first measles outbreak in L.A. County since the one that began at the Disney theme parks in Dec. 2014. By the time that outbreak was contained in April 2015, the California Department of Public Health had confirmed 136 cases statewide.

That outbreak shined a light on low vaccination rates in some communities, as the state reported that at least 57 of those infected were not vaccinated against measles. It also spurred the passage of a state law that eliminates parents' right to opt out of vaccinating their children due to personal or religious beliefs.

As the measure moved through the Legislature, it drew angry opposition from vaccination skeptics and those who object to the federal government's vaccination schedule. After Gov. Brown signed it into law, it survived a court challenge. The legislation took effect this school year.

The law only applies to kids entering school for the first time – including those starting day care or kindergarten, or those who are new to the state – and kids entering seventh grade. It grandfathers in students who are already enrolled in school and already have vaccine exemptions based on personal beliefs or religion – at least until they reach seventh grade.

People with measles typically develop a fever, runny nose, cough and a rash all over the body. In some people, measles can cause pneumonia, encephalitis or death.

The highly contagious disease can live for up to two hours on a surface or in the air in an area where an infected person coughed or sneezed.

If one person has the disease, 90 percent of the people close to that person who are not immune will also become infected, according to health experts. A person can develop measles up to 21 days after being exposed to someone else who has the disease.

Infected people are usually contagious from four days before they develop a telltale rash to four days afterward.