SAN JOSE — An international traveler infected with measles visited 20 places across the South Bay — including the Apple Park Visitor Center in Cupertino, Hoover Tower at Stanford and the Great Mall in Milpitas — over an eight-day period, triggering a Santa Clara County warning of possible public health exposure.

People who were at the same stores, restaurants or other visitor attractions as the infected person was between March 16 and 23 and who haven’t been vaccinated or had measles before should watch for symptoms of the highly contagious respiratory disease, including a high fever, runny nose, cough, and red eyes, followed by a rash that spreads all over the body.

“You can’t really know who was in these places and who might be susceptible. What I can tell you is the vaccination rates are quite high, and the number of people who might’ve been susceptible is probably pretty low,” Dr. Sara Cody, county health officer and public health director, said in an interview Tuesday afternoon.

Cody said public health officials usually contact places or individuals who might have been exposed to measles without issuing a public health notice. But in this case the agency has no way of narrowing down who might have been potentially exposed. “The reason we put this (public notice) out is because the person with measles did a lot of sight seeing … this infectious traveler was very ambitious.”

She said those most at risk are infants too young to be vaccinated or people who chose not to be, as well as people with a medical condition. Infants are usually vaccinated between 12 and 15 months, although babies younger than six months cannot be vaccinated.

It’s unclear whether the infected person, who is receiving treatment at a hospital, was vaccinated.

County officials declined to answer questions about what country that person was traveling from or whether he or she traveled with others who might also have been exposed, citing health privacy laws.

The county says this case of measles is not related to a recent cluster of three cases in which two people from Santa Clara and San Francisco counties contracted measles from a Santa Cruz County resident in a February international flight that landed at San Francisco International Airport. It’s unclear whether that person knew he or she had measles at the time.

Meanwhile, health officials in Shasta County on Sunday said a measles case reported there was related to two others reported in Butte and Tehama counties, according to the Redding Record-Searchlight.

The Shasta woman who came down with measles apparently caught it from her father, who contracted the illness while traveling overseas.

Dates, time and places where people may have been exposed to measles:

Saturday, March 16

9 – 11 a.m.​ | T Mobile Store, 789 El Camino Real, Sunnyvale

9:30 a.m. – 12 noon​ | International House of Pancakes, 644 North First St, San Jose

11 a.m. – 1:30 p.m. ​| Apple Visitor Center, 10600 N Tantau Ave, Cupertino

12:30 – 3:30 p.m. ​| Hoover Tower Observation Deck, Stanford University, 550 Serra Mall, Stanford

1:30 – 4 p.m.​ | Poki Bowl, 2305 El Camino Real, Palo Alto

3 – 5 p.m.​ | Walmart, 600 Showers Dr, Mountain View

4 – 6:30 p.m.​ | The Fish Market, 3775 El Camino Real, Santa Clara

6 – 8 p.m.​ | Macy’s Valley Fair Mall, 2801 Steven’s Creek Blvd, Santa Clara

9 – 11 a.m.​ | T Mobile Store, 789 El Camino Real, Sunnyvale 9:30 a.m. – 12 noon​ | International House of Pancakes, 644 North First St, San Jose 11 a.m. – 1:30 p.m. ​| Apple Visitor Center, 10600 N Tantau Ave, Cupertino 12:30 – 3:30 p.m. ​| Hoover Tower Observation Deck, Stanford University, 550 Serra Mall, Stanford 1:30 – 4 p.m.​ | Poki Bowl, 2305 El Camino Real, Palo Alto 3 – 5 p.m.​ | Walmart, 600 Showers Dr, Mountain View 4 – 6:30 p.m.​ | The Fish Market, 3775 El Camino Real, Santa Clara 6 – 8 p.m.​ | Macy’s Valley Fair Mall, 2801 Steven’s Creek Blvd, Santa Clara Sunday, March 17

9:30 a.m. – 12:30 p.m.​ | Bill’s Café, 3163 Middlefield Rd, Palo Alto

6 – 9 p.m.​ | Cascal, 400 Castro St, Mountain View

7:30 – 9:30 p.m.​ | 7-Eleven, 848 E. Evelyn Ave, Sunnyvale

9:30 a.m. – 12:30 p.m.​ | Bill’s Café, 3163 Middlefield Rd, Palo Alto 6 – 9 p.m.​ | Cascal, 400 Castro St, Mountain View 7:30 – 9:30 p.m.​ | 7-Eleven, 848 E. Evelyn Ave, Sunnyvale Monday, March 18

7 – 10 p.m.​ | Il​ Fornaio (Cucina Italiana), 2752 Augustine Dr, #120 Santa Clara

10 – 11:30 p.m.​ | 7-Eleven, 848 E. Evelyn Ave, Sunnyvale

7 – 10 p.m.​ | Il​ Fornaio (Cucina Italiana), 2752 Augustine Dr, #120 Santa Clara 10 – 11:30 p.m.​ | 7-Eleven, 848 E. Evelyn Ave, Sunnyvale Tuesday, March 19

7 – 9:30 p.m.​ | Great Mall, 477 Great Mall Drive, Milpitas

9:30 – 11 p.m.​ | Seniore’s Pizza, 940 Monroe St, Santa Clara

7 – 9:30 p.m.​ | Great Mall, 477 Great Mall Drive, Milpitas 9:30 – 11 p.m.​ | Seniore’s Pizza, 940 Monroe St, Santa Clara Wednesday, March 20

7 – 9:30 p.m.​ | SA-BY Thai Cuisine, 404 S. 2nd St, San Jose

9 – 10:30 p.m.​ | Lucky, 3705 El Camino Real, Santa Clara

7 – 9:30 p.m.​ | SA-BY Thai Cuisine, 404 S. 2nd St, San Jose 9 – 10:30 p.m.​ | Lucky, 3705 El Camino Real, Santa Clara Thursday, March 21

7:30 – 9:30 p.m.​ | CVS Pharmacy, 1165 El Camino Real, Sunnyvale

7:30 – 9:30 p.m.​ | CVS Pharmacy, 1165 El Camino Real, Sunnyvale Friday, March 22

4:30 – 6:30 p.m.​ | Safeway, 645 San Antonio Rd, Mountain View

5:30 – 7:30 p.m.​ | CVS Pharmacy, 1675 Hollenbeck Ave, Sunnyvale

Measles symptoms can appear seven to 21 days after exposure. Anyone who develops symptoms should contact a doctor right away and call ahead to a medical facility to let it know of the exposure.

“The keys are: Know what the symptoms are, know how long to watch for them, and then (if you show symptoms), call your provider,” Cody said. “Don’t just go in. You don’t want to go into urgent care and infect everybody.”

The distinct rash that accompanies measles, which begins on the face before spreading to the rest of the body, begins to appear three to five days after symptoms begin; infected people are contagious from four days before through four days after the rash appears, according to the Centers for Disease Control website.

The measles virus lives in nose and throat mucus of an infected person and can spread through coughing and sneezing. The virus can live for up to two hours in the air where an infected person coughed or sneezed, according to the CDC, and is so contagious that up to 90 percent of people close to an infected person who aren’t immune will also become infected.

The disease also can cause pneumonia, vision loss, severe diarrhea and even death, killing 136,000 people worldwide in 2017, including many young children, according to the World Health Organization.

Vaccination rates among children in Santa Clara County are high, over 97 percent on average in public schools and over 94 percent on average in private schools, according to the county website, although the rate varies among individual schools.

Statewide, 96.9 percent of kindergartners are vaccinated, compared to 92.2 percent before a 2016 law that requires all children to be vaccinated before entering kindergarten and eliminating a “personal belief” exemption.

The MMR vaccine, an abbreviation for measles, mumps and rubella, is considered highly effective. Two doses are 97 percent effective at preventing measles while one dose is about 93% effective, according to the CDC.

Read the full warning on the county website. The public health department provides vaccinations, including the measles vaccine, which are usually covered by insurance.