Health officials recorded no new cases of measles in the United States last week, marking the first week without new cases of the disease since January, amid an outbreak largely linked to parents who declined to vaccinate their children.
The U.S. Centers for Disease Control and Prevention said on Monday it had recorded 1,241 cases of the highly contagious and sometimes deadly disease in 31 states as of last Thursday.
The current outbreak of measles is the worst to hit the country since 1992, when 2,126 cases were reported, and threatens to end the nation’s measles-free status.
The outbreak began in New York on Oct. 1, 2018, but the CDC did not begin publicly reporting weekly new cases for several months. In one week in January, the agency recorded no new cases but did not report that information publicly, according to CDC spokeswoman Kristen Nordlund.
“While this outbreak of a preventable disease illustrates the significant public health threat posed by willful disregard of the efficacy and science of vaccination, the Department’s pro-vaccine message is clearly resonating,” the New York State Department of Health said in a statement.
More than 71,000 doses of MMR vaccines have been administered in the New York counties affected by the outbreak since last October, which is a 70% increase from the previous year, the department said.
The majority of U.S. measles cases this year have occurred in children who had not received the measles-mumps-rubella vaccine, which confers immunity to the disease.
Federal health officials have attributed the outbreak in large part to a vocal fringe of U.S. parents who refuse to vaccinate their children because they believe, contrary to scientific evidence, that ingredients in them can cause autism.
U.S. Health and Human Services Secretary Alex Azar told reporters in April that the current outbreak “is completely avoidable” and the unfortunate result of some people’s choice to deny the proven safety of vaccines.
The weekly increase in the number of cases has tapered down over the past few months, dropping to seven new cases two weeks ago. The report of zero new cases last week was the latest indication the outbreak is petering out after dozens of cases were reported per week earlier this year.
An outbreak is typically considered over when there are no new measles cases reported for 42 days, which is double the incubation time for the disease, Nordlund said.
The disease was declared eliminated in the United States in 2000, meaning there was no continuous transmission of the disease for a year. Still, cases of the virus occur and spread via travelers coming from countries where measles is common.
CDC officials have warned that the country risks losing its measles elimination status if the outbreak in New York lasts for more than a year.