The health department said they are taking all precautionary measures to prevent the disease from spreading. The outbreak in Clark County has been concentrated mostly among unvaccinated children.
Across the US, 10 states - California, Colorado, Connecticut, Georgia, Illinois, New Jersey, New York, Oregon, Texas and Washington - reported 79 confirmed measles cases in January, according to the Centers for Disease Control and Prevention.
The department did not release any information about the person who contracted measles, citing patient confidentiality.
Demand for measles vaccine has surged in Clark County, where the highly contagious virus is linked to more than 50 confirmed illnesses this year - including among people who had previously shunned the shots.
As they bring awareness locally to the community, Espinoza said, her public health counterparts in southeast Texas are trying to pinpoint the reason behind the cases there.
"Clark County Public Health is urging anyone who has been exposed at an identified location and believes they have symptoms of measles to call their health care provider prior to visiting the medical office to make a plan that avoids exposing others in the waiting room", the agency said. Health officials have long anxious about the potential for an outbreak in the region.
Health officials are encouraging everyone to protect themselves from the virus by being vaccinated. The CDC notes that two doses of the MMR vaccine are 97 percent effective, while one dose is 93 percent effective.
"The measles vaccine isn't ideal, but one dose is 93 percent effective at preventing illness", Dr. Alan Melnick, Clark County's health officer, said in a statement.
That's a huge rise in a county where vaccination rates lag - only 76.5 percent of kindergartners had all the required immunizations for the 2017-18 school year.
Symptoms include a high fever, coughing, runny nose and watery, red eyes between seven and 14 days after infection, the U.S. National Library of Medicine says.