On Monday, officials in Clark County in southwestern Washington state are expected to declare the measles outbreak there over, NBC News has confirmed. It has been 42 days since the last confirmed measles case in the county, and public health officials are not currently investigating any suspected infections.

The announcement is conditioned on there being no new infections reported over the weekend.

Since January, there have been 73 confirmed cases in Clark County, mostly children under 10. The incubation period for the highly contagious respiratory disease is seven to 21 days. "We wanted to wait for two full incubation periods," a spokesperson for the Clark County public health department told NBC News.

The Centers for Disease Control and Prevention reported this week that measles cases in the U.S. have reached the highest number since the disease was eliminated in 2000.

Clark County, a suburb of Portland, Oregon, had been the epicenter of measles in Washington state and most of the patients had not received their mumps, measles and rubella shots. As the number of cases rose earlier this year, Gov. Jay Inslee of Washington declared a state of emergency, hundreds of students in Clark County were ordered to stay home after exposure to the virus and health clinics gave free vaccines to thousands of students.

"The fact that now there are no new measles cases in Clark County, Washington, says a lot about the commitment and perseverance of the local and state health departments," pediatrician Dr. Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine, told NBC News via email. "They should be congratulated."