U.S. Officials Address Measles Outbreaks

CHICAGO, Jan 6 – U.S. health authorities are trying to establish that the ongoing measles outbreaks in South Carolina and other states are not linked to last year’s significant outbreak in Texas. This effort is crucial for maintaining the nation’s claim of having eliminated the disease, particularly after experiencing the highest number of confirmed cases in the past three decades.

To meet the criteria set by the World Health Organization for being deemed measles-free, a country must have no locally transmitted cases of the same strain for at least 12 consecutive months.

Experts studying this issue are cautioning that the assessment of elimination may not be foolproof. They argue it can be quite challenging to ensure that all cases potentially associated with the Texas outbreak have been documented accurately.

A significant outbreak started in Texas in January 2025, which then spread to several other states. Subsequent outbreaks also took place near the Arizona-Utah border and in South Carolina, continuing to pose a risk for further infections.

In November, the Pan American Health Organization stated that Canada had lost its measles elimination status after struggling to contain a year-long outbreak of the disease, which is preventable by vaccination.

This year, PAHO will scrutinize U.S. measles data, which currently includes 2,065 confirmed cases, to determine if the U.S. can retain its elimination status held since 2000. Measles elimination is seen by former public health officials as a significant measure of a country’s health standards.

Proving Unrelated Outbreaks

The U.S. must demonstrate that the current measles cases are not tied to the Texas outbreak, but rather stem from infected travelers, according to William Moss, an epidemiology professor at Johns Hopkins Bloomberg School of Public Health.

Public health officials are employing both traditional interview techniques with infected individuals and genetic comparisons of the virus to identify transmission chains. However, experts are concerned this may not suffice for tracing cases in larger outbreaks.

Kelly Oakeson, who oversees next-gen sequencing at the Utah Public Health Laboratory, indicated that while none of the patients interviewed in Utah reported traveling to Texas or having contact with anyone from there, many provided unclear information.

Based on Utah’s genetic analysis, Oakeson noted that the strain there is “different enough” from the Texas outbreak, suggesting a lack of direct connection. Preliminary findings from the CDC analysis, which have not yet been published, seem to support this notion.

In a December 5 post, CDC Acting Director Jim O’Neill stated that no epidemiological evidence links the Texas outbreak to the ongoing cases in South Carolina.

A spokesperson from the U.S. Health and Human Services confirmed that no linkage has been found. However, many recent U.S. cases share the same viral genotype without known sources, which suggests potential ongoing domestic transmission.

Potential Gaps in Reporting

Dr. Noel Brewer, an infectious disease specialist at the University of North Carolina, observed that the evidence indicates new cases in Texas ceased in July, with a three-week gap before the Utah-Arizona outbreak emerged. He noted that no clear connections have surfaced between these outbreaks.

Brewer, who leads an independent committee to examine the data, pointed out that the CDC’s inability to link outbreaks may reflect how widely the virus is circulating in the U.S. He suggested that tracking all cases accurately is currently unfeasible.

There are significant gaps in understanding the U.S. outbreaks, with not all cases being reported or identified, said Moss from Johns Hopkins. He warned that this could lead to missed connections between outbreaks, especially since some of the larger outbreaks are occurring in communities that may distrust public health systems.

Dr. Demetre Daskalakis, former director at the CDC’s National Center for Immunization and Respiratory Diseases, emphasized that PAHO will base its decision on the available evidence. If there are compelling reasons to doubt the data’s integrity, the U.S. could indeed lose its measles elimination status.