Another unvaccinated child under 11 years old is the 23rd person to have measles in a Clark County outbreak.

The county public health department said Tuesday that two more people are suspected of having measles and identified four more locations where people might have been exposed to the disease.

Kaiser Cascade Park Medical Office, 12607 SE Mill Plain Blvd., Vancouver from 12:30 to 7:30 pm Saturday, Jan. 19

Dollar Tree, 7809-B Vancouver Plaza Drive, Vancouver from 6:30 to 9:10 pm Tuesday, Jan. 15

Portland International Airport, baggage claim and south end of the ticket counter (near Alaska Airlines and Starbucks), 7000 NE Airport Way, Portland from 7:30 to 11 pm Tuesday, Jan. 15

Costco, 4849 NE 138th Ave., Portland from 5:30 to 8:40 pm Wednesday, Jan. 16

On average, more than one person a day has been diagnosed with measles since Jan. 1 in an unusually large outbreak.

Of the 23 people who have measles, 18 of those are 10 years old or younger. Only one is an adult.

Nearly all never received a vaccine against measles. One person has been hospitalized.

The highly contagious virus spreads through the air and can linger for up to two hours in an isolated space. People who have never received a measles vaccine are susceptible to the disease, which can at times be deadly.

The measles vaccine is highly effective. People can get a precautionary measles shot now or even within 72 hours after exposure to the virus and likely be OK.

This outbreak has hit the Evergreen School District in Clark County especially hard. Clark County has one of the worst vaccination rates in Washington with just 77.4 percent of all public students in the Vancouver area having completed their vaccinations, state records show.

Clark County health officials are keeping both students and staff who cannot prove they have been vaccinated from the schools linked to the outbreak. Those who are excluded are also not supposed to enter other schools, child care centers or places with lots of people.

Even friends and families of students and staff at Evergreen High School and Orchards, Hearthwood and Image elementary schools are asked not to attend any events or games at the schools unless immunized. The Clark County health department has placed this restriction until Jan. 30 for most schools and Feb. 5 for Orchards.

To further limit the spread of the virus, health officials ask that people who think they might have measles call their doctor or health care provider before physically visiting a hospital or doctor’s office.

Due to the size of the outbreak, the public health department will send an automated call starting Tuesday to people who have been identified as possibly exposed to measles. Not everyone who may have been exposed will receive the call.

The call will come from the Clark County call center at 360-397-8021. Most people will be called at 10:30 a.m. There will be a second round of calls at 1 p.m. for people not reached the first time. The recording will gather information about whether the person who is called has shown symptoms of measles.