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ARUP’s assay is the first commercially available reference test that both detects the measles virus and distinguishes between vaccine-related and wild-type strains of the virus.
ARUP Laboratories’ dual-target molecular measles virus assay provides a highly sensitive, specific, and rapid assay to aid the public health response to ongoing measles outbreaks. An article describing the development of ARUP’s assay, Development of a Dual-Target Measles Virus PCR Assay and Testing Trends at a National Reference Laboratory, has been published in the Journal of Clinical Microbiology.
In April 2025, ARUP launched the assay in response to ongoing measles virus outbreaks, including a large cluster in Texas that began in early 2025. The assay is the first commercially available reference test that both detects the measles virus and distinguishes between vaccine-related and wild-type strains of the virus. This differentiation helps providers quickly determine which cases are active infections so they can pursue the appropriate patient management strategies.
The measles, mumps, and rubella (MMR) vaccine uses a live, attenuated form of the measles virus. As a result, approximately 5% of individuals who receive the vaccine may develop a measles-like rash that can be mistaken for active infection.
“The vaccine virus is not transmissible. Patients with a vaccine-related rash can go about their day,” said Benjamim Bradley, MD, PhD, ARUP medical director. “For patients with active infections, steps need to be taken to limit spread of the virus by isolating the patient and investigating any exposure events. Having those data at the time of diagnosis is important.”
Bradley is medical director of High Consequence Pathogen Response, Virology, and Molecular Infectious Diseases at ARUP, and he oversaw the development of the molecular measles assay.
The CDC reported 2,242 total confirmed measles virus cases for the year 2025. This represents the highest number of cases in a single year since 1992. Seventy percent of cases in 2025 occurred in children and adolescents 19 years or younger. Measles outbreaks have continued into this year; nine states have ongoing outbreaks.
The measles virus is highly infectious. For individuals who are unvaccinated and exposed to the virus, the likelihood of infection is 90%.
“In terms of vaccination coverage, we need about 95% to be able to prevent the spread of measles virus,” Bradley said.
While the majority of individuals infected recover from measles within 10 days, severe cases can result in respiratory failure, pneumonia, and brain inflammation, especially in young children. Even in mild cases, measles virus infection can have long-term effects.
A 2019 study found that measles virus infection reduces immunity to other infections.
“The study found that antibodies to different pathogens, across the board, decreased anywhere from 15% to 70% after measles virus infection,” Bradley said. “Measles doesn’t just cause respiratory illness; it also attacks your immune system.”
The long-term effects of measles infection on immunity can also be seen in larger populations.
“Following the outbreak of measles virus in a country or area, there’s a disproportionately higher number of deaths tied to infectious disease for the next five years or so,” Bradley said.
A rare but deadly complication known as subacute sclerosing panencephalitis (SSPE) can occur years later.
“SSPE happens five to 10 years after a measles infection. It’s a rapidly progressive condition that leads to neurological dysfunction. It’s uniformly fatal, and young children, particularly those younger than 2 years, are at highest risk for this complication,” Bradley said. “This is a very rare but tragic outcome.”
The Associated Press reported that a school-age child died as a result of SSPE last September. The child had contracted measles as an infant.
The ARUP study on testing trends published in the Journal of Clinical Microbiology found that molecular, or polymerase chain reaction (PCR), testing was ordered less frequently than serology testing, which may indicate that PCR testing is an underutilized resource. PCR tests amplify viral genetic material to detect the presence of the virus, while serology testing is used to detect antibodies, which the body produces in response to an infection.
“Molecular testing provides more sensitivity and specificity than the serology tests during the early, acute phase of infection,” Bradley said.
During the time period in which the study was conducted, ARUP provided results for the PCR measles assay in 27 hours, on average, demonstrating the test’s efficacy in delivering rapid results to aid providers with treatment and quarantine decisions.
“We made the decision to develop a dual-target measles assay because we know it is important for public health and to support providers and patients across the U.S.,” Bradley said. “This decision speaks to our commitment to do what’s right for the patient.”
Kellie Carrigan, kellie.carrigan@aruplab.com
