The number of measles diagnoses in California has grown to 19 as of April 5, a CapRadio analysis of state and county public health reports shows.

Butte County experienced a particular bump over the weekend as the total number of cases in the county rose to six on April 5, according to the Butte County Department of Public Health. Butte County currently has the highest number of cases of any California county, with Placer and Santa Clara counties following it with three cases each.

Butte County also has the highest number of cases per capita, with about three diagnoses for every 100,000 residents according to the 2017 population count.

Calaveras County, which has a population of 44,656 according to the 2017 count, as one reported case of measles. The other counties with reported infections are Placer, Los Angeles, San Francisco, Santa Clara, Santa Cruz, San Mateo and Tehama counties.

CDPH Division of Communicable Disease Control Chief Dr. James Watt told CapRadio in late March that the department is “very concerned” with the rising number of measles cases in the first part of 2019. There were a total of 21 confirmed cases of measles in California over the whole of 2018, according to the state Department of Public Health.

California last saw a large measles outbreak in December 2015 to April 2015, when at least 131 residents were infected, according to CDPH. The outbreak was associated with Disneyland and also impacted residents of six other states.

According to the Center for Disease Control and Prevention, a measles infection typically begins with a high fever, cough, runny nose, and watery eyes, followed by tiny white Koplik spots inside the mouth, and then a skin rash. It’s highly contagious, with up to 90% of non-immune individuals developing infections.

In 1963, before a vaccine was available, nearly all children were infected before age 15 and as many as 3 to 4 million people were infected every year. On an annual basis it once caused 400 to 500 deaths, with about 1,000 cases of encephalitis (swelling of the brain) and 48,000 hospitalizations.

The CDC started a campaign in 1978 to eliminate measles from the US. By 2000, the vaccination program had effectively eliminated measles with no continuous disease transmission for more than 12 months.

Most of the reported measles illnesses in California in 2019 are in young children. More than 400 cases have been reported nationally this year.

UC Davis Children’s Hospital Chief of Pediatric Infectious Diseases Dr. Dean Blumberg and Dr. Andy Miller from Butte County Public Health joins Insight to talk about how measles is spread and what steps you can do to prevent infections in your family and your community.