Clinical Performance and Trends during the First Two Months of Monkeypox Virus PCR Testing at Two United States...

Area of Science:

• Virology
• Epidemiology
• Public Health

Background:

• A human-to-human monkeypox virus (MPXV) outbreak emerged globally in 2022.
• US MPXV testing expanded from public health labs to clinical settings.
• Understanding testing characteristics is crucial for outbreak management.

Purpose of the Study:

• To analyze epidemiological features of MPXV testing.
• To evaluate specimen collection practices and cycle threshold (Ct) values.
• To inform optimal testing strategies during the MPXV outbreak.

Main Methods:

• Retrospective analysis of 10,019 MPXV PCR tests from two reference laboratories.
• Examination of demographic data, positivity rates, and Ct values.
• Comparison of results based on collection method and number of specimens.

Main Results:

• High positivity rates observed in men and individuals aged 30-49.
• Overall positivity rate remained elevated (~20%) but decreased over time.
• Significant differences in Ct values noted between laboratories and collection methods.
• High concordance (>95%) when multiple specimens were collected per individual.
• Individuals aged 50-59 showed distinct viral load distribution, possibly due to prior vaccinia vaccination.

Conclusions:

• Early US MPXV testing data highlights key demographic trends.
• Ct value variations suggest impact of specimen processing and collection.
• High concordance supports limiting the number of swabs per individual to optimize resource allocation.
• Further research into age-related viral load differences is warranted.