A teenager with measles was infectious when she visited Disneyland, Universal Studios and other heavily visited sites in Southern California earlier this month, public health officials said.

The teen was on a trip from New Zealand and flew into Los Angeles International Airport. She visited Disneyland and California Adventure, among other attractions from August 11 to 15.

She also reportedly traveled to Universal Studios, Madame Tussauds and the Santa Monica Pier during the trip, the officials said.

Public health officials in Los Angeles and Orange counties said Friday they are attempting to find anyone who might have been exposed to the virus and has started showing symptoms.

Measles is one of the most contagious viruses in the world. Around 90 percent of unvaccinated people exposed to the virus will contract the disease within seven to 21 days.

And those infected can transmit the virus to another person four days before and four days after its telltale rash appears, health officials said.

"Measles is spread by air and by direct contact even before you know have it," Muntu Davis, Los Angeles County's health officer, said in a statement. The potentially severe disease causes fever, rash, cough, and red, watery eyes.

According to the health agencies in Los Angeles and Orange counties, the teen visited Disneyland on August 12 and Universal on August 14.

The average daily number of visitors at Disney was around 45,000 in 2015,according to the Los Angeles Times. Universal Studios had a record-high daily visitor count of 40,000 in 2017, the Times reported.

The infected teen was in Terminal 8 at LAX on the evening of August 11 and at the Tom Bradley International Terminal on the evening of August 15.

The CDC reported 1,203 individuals cases of measles in 30 states through Aug. 15, which was an increase of 21 cases from the previous week. This is the largest measles outbreak in the United States since 1992, and since measles was declared eliminated in 2000.

New Zealand is also struggling with a measles outbreak. Through mid-August, it had confirmed 639 cases of measles cases this year.

As officials continue to investigate, the California Department of Public Health said it wasn't aware of measles cases stemming from exposure to the teen, the AP reported.

Jeffrey Gunzenhauser, chief medical officer for the LA County Department of Public Health, said that although no one has reported contracting measles yet, individuals might not be showing symptoms.

"If we do have cases here in LA county as a result of this, I would expect that we would see them at the end of next week or next weekend," Gunzenhauser said Saturday.

The department is retracing the teenager's steps to locate people she might have come into contact with, like servers at a restaurant, and making sure they are immunized, either through vaccine records or a blood test, Gunzenhauser said.

If they cannot prove immunization, health officials can order them to stay out of public spaces to stem the potential spread.

Measles, a virus that was eliminated in the United States some 20 years ago, has sprung back in recent years in many countries around the world, including the US Outbreaks have been fueled in many countries, including the United States, by mistrust and misinformation campaigns about vaccine safety.

"Measles is a highly contagious and potentially severe disease that causes fever, rash, cough, and red, watery eyes," Nichole Quick, the Orange County health officer, said in statement. She urged everyone to seek an immunization if they had not already done so.

"We maintain rigorous sanitation standards to protect guests and cast, and earlier this year we strengthened our immunization program and educational resources for cast members, in addition to our ongoing efforts," Pamela Hymel, chief medical officer of Disney Parks, said in a statement on Friday.

Audrey Eig, a spokesperson for Universal Studios Hollywood, said studio officials "have been advised by the Department of Public Heath that there is minimal risk to any exposure at our destination."

A 2015 measles outbreak linked to Disneyland led to 147 cases in multiple states as well as in Mexico and Canada. Many of those who were sickened were unvaccinated or did not know their vaccine record, according to the Centers for Disease Control and Prevention.

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