Objective Epidemiological evidence was systematically reviewed to determine how long the measles virus remains transmissible after an infectious case leaves a public space to address inconsistencies in measles contact tracing exposure window guidelines.

Methods A systematic literature review following PRISMA guidelines was conducted using PubMed, EMBASE, Web of Science, and SCOPUS databases for publications from January 1988 to July 2024. Additional sources were identified through reference list reviews and Google Scholar searches. Studies examining how long the measles virus survives in the air or remains transmissible after an infectious case leaves a public space were included, while non-evidence-based recommendations and mathematical models were excluded.

Results Initial database searches identified 1,054 studies, with none meeting initial inclusion criteria after screening. Supplemental searches identified five relevant articles (1964-1987). Two experimental studies demonstrated measles virus survival between 30 and 120 minutes, with increasing survival time for lower humidity levels. Experimental studies showed survival at two hours in low humidity (12-15%), up to 60 minutes in moderate humidity (36-37%), and 30 minutes in high humidity (60-70%) at 20°C. Three publications reviewed how long measles virus was transmissible in real-world settings, ranging from 60 to 120 minutes.

Conclusions Limited evidence exists to guide the precise determination of the duration of measles transmissibility. Current health department guidelines rely on limited research from 1964 to 1987. Additional studies are needed to understand how long the virus is transmissible in real-world settings, particularly given the implications for contact tracing efficiency and resource allocation during outbreak responses.

SUMMARY BOX

What is the current understanding of this subject?

The current understanding of how long the measles virus remains transmissible in the air is based on limited research from 1964-1987, with CDC guidelines recommending a two-hour exposure window while some health departments use a one-hour window.

What does this report add to the literature?

This report adds a comprehensive systematic review that confirms the scarcity of evidence on measles virus transmissibility in air, highlighting that no new research has been published since 1987 to inform contact tracing guidelines.

What are the implications for public health practice?

The implications for public health practice include the need for new research to standardize evidence-based guidelines for measles contact tracing, which would optimize resource allocation during outbreak responses, potentially reduce unnecessary interventions, and help foster trust in public health activities.

The authors have declared no competing interest.

This analysis was supported by the U.S. Centers for Disease Control & Prevention (Cooperative Agreement #NU38FT000004).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

All data used in this study were publicly available published articles.

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FUNDING This analysis was supported by the U.S. Centers for Disease Control & Prevention (Cooperative Agreement #NU38FT000004).

ETHICAL STATEMENT Interviews cited within this systematic review informed its basis and were approved by the Institutional Review Board at the Johns Hopkins Bloomberg School of Public Health (IRB #00028357) and not considered human subjects research.

All data produced in the present study are available upon reasonable request to the authors