Caitlyn Stulpin , 2025-04-22 18:27:00
April 22, 2025
3 min read
Key takeaways:
- One in five blood donors from endemic areas had evidence of Jamestown Canyon virus infection.
- The proportion of donors with neutralizing antibodies increased with older age.
The baseline seroprevalence of Jamestown Canyon virus antibodies in blood donated by people living in endemic areas was relatively high, researchers found in a study.
“Overall, we recognized a need for a clearer baseline estimate of Jamestown Canyon virus antibodies in people living in areas where this virus was more common so we could better guide recommendations for diagnostic testing and interpretation of results,” Rebekah Sutter, MPH, BSN, RN, an Epidemic Intelligence Service officer with CDC’s Division of Vector-Borne Diseases, told Healio.
Data derived from Sutter RA, et al. Clin Infect Dis. 2025;doi:10.1093/cid/ciaf131.
“Testing blood donations in these areas would help determine how many people have antibodies from a previous infection with Jamestown Canyon virus and not an active infection,” she said.
Rebekah Sutter
According to Sutter, they repeatedly saw serological test results showing that symptomatic patients were positive for Jamestown Canyon virus, but their symptoms were more likely related to something else, such as another arbovirus, which “makes it difficult to accurately interpret diagnostic results.”
“In some cases, coinfection wasn’t likely, so we sought to understand if baseline seroprevalence in endemic areas could be impacting the results of this testing,” Sutter said.
She explained one example of a case where a patient tested positive for both Powassan virus and Jamestown Canyon virus antibodies, although she said it was unlikely to be a coinfection as these two viruses are transmitted by two different vectors and the patient’s symptoms occurred at a time of year when mosquitoes were less active in the area.
“It was more likely that they still had antibodies from a prior asymptomatic Jamestown Canyon virus infection, but their current symptoms were due to Powassan virus,” she said.
To better understand baseline prevalence of neutralizing and IgM antibodies, the researchers used randomly selected blood donations collected between December 2019 and April 2020 from people living in counties reporting at least two cases in 2019 or one case in 2019 and at least one case between 2010 and 2018.
According to the study, the specimens were screened for Jamestown Canyon virus-specific neutralizing antibodies and were then tested for IgM antibodies if they tested positive. Using these data, the researchers then estimated seroprevalence at the population level by applying sample weights calibrated to the population age group distributions from the 2020 United States Census Bureau data.
Overall, 14 counties in Massachusetts, Minnesota and Wisconsin met the study’s inclusion criteria. From these counties, a total of 355 specimens were tested with approximately one in five having evidence of prior infection. Among them, 64 were positive for Jamestown Canyon virus infection and, of those 64, 38 also tested positive for Jamestown Canyon virus-specific IgM antibodies.
Within each state, average county seroprevalence for Jamestown Canyon virus neutralizing antibodies ranged from 16.8% (95% CI, 9.3%-27%) in Massachusetts to 18% in Wisconsin (95% CI, 10.9%-27.1%) and 18.8% (95% CI, 14%-24.4%) in Minnesota, whereas average county seroprevalence for both neutralizing and IgM antibodies was 7.6% (95% CI, 4.2%-12.5%) in Wisconsin to 9.3% (95% CI, 3.8%-18.3%) in Massachusetts and 13.5% (95% CI, 9.6%-18.3%) in Minnesota.
According to the study, the highest seroprevalence estimates were seen in the two counties in which samples were not available from young blood donors — St. Louis County in Minnesota (91%; 95% CI, 70.9-99) and Marathon County in Wisconsin (47.2%; 95% CI, 15.7-80.5%).
The researchers added, though, that there was no trend in the percentage of donors testing positive for Jamestown Canyon virus-specific IgM antibodies but that the proportion with Jamestown Canyon virus neutralizing antibodies increased with older age.
Based on these results, Sutter concluded that the “relatively high” baseline seroprevalence of Jamestown Canyon virus antibodies in endemic areas “emphasizes the need to consider the probability of a patient’s prior infection when testing and interpreting diagnostic results.”
“Detection of Jamestown Canyon virus antibodies might not correlate with acute illness, especially in older patients,” Sutter said. “If your patient has a clinically compatible illness, exposure history and lack of an alternative diagnosis, an active infection with Jamestown Canyon virus infection is more probable.”
She added, however, that if the patient has compatible symptoms but lacks exposure history and other diagnoses are possible, it’s likely more probable that they have lingering antibodies, rather than an acute infection with Jamestown Canyon virus.
“Understanding this is important for improving diagnosis and public health surveillance of Jamestown Canyon virus disease,” Sutter said. “The gold standard of serologic diagnosis of recent infection should be to test acute and convalescent sera to assess for [at least a] 4-fold change in neutralizing antibody titer.”
For more information
Rebekah Sutter, MPH, BSN, RN, can be reached at media@cdc.gov.
Sources/Disclosures
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Disclosures:
One author reports being an executive board member of the Council of State and Territorial Epidemiologists. The other authors report no relevant financial disclosures.
