Secondary Monkeypox Transmission Unlikely in Community, Health Care Settings

The lack of secondary spread of monkeypox suggests pre-exposure prophylaxis may not be necessary for most health care professionals at risk for monkeypox exposure.

Results of a contact tracing investigation found no evidence of secondary spread of monkeypox virus infection among 166 community members and health care professionals (HCP) were exposed to the first patient diagnosed with the infection in the United States. These study findings were published in Annals of Internal Medicine.

This study was conducted by investigators at Massachusetts Department of Public Health. Household, workplace, and HCP contacts who interacted with the index patient were identified through multiple interviews and review of records and schedules. Individuals at high or intermediate risk for monkeypox infection were recommended to receive postexposure prophylaxis (PEP). All contacts were monitored for symptoms over a 21-day period following exposure. The primary outcome was the diagnosis of secondary monkeypox infection.

During the index patient’s infectious period, a total of 166 contacts were identified. In the community, 4 individuals interacted with the patient prior to symptom onset. Other individuals who interacted with the index patient included 2 household contacts, 35 workplace contacts, and 129 HCPs across 4 facilities.

Contacts were stratified into 4 risk categories, including those whose exposure risk was either high, intermediate, or low or uncertain, as well as those considered to not be at risk for exposure. A total of 4 individuals were considered at high risk for secondary monkeypox transmission, of whom 2 were HCPs and 2 were fellow patients. The remaining individuals were categorized as having intermediate or low risk for exposure.

Public health authorities and health care facilities should consider how these findings may inform revised estimates of exposure risk, requirements for monitoring and recommendations for PEP.

All individuals considered to be at high risk for exposure were offered PEP, of whom 3 accepted treatment. Of the 10 individuals at intermediate risk for exposure who were eligible for and were offered PEP, 2 accepted treatment.

All contacts were monitored for signs and symptoms consistent with monkeypox infection for 21 days. A total of 13 HCPs, 2 community members, and 2 fellow patients developed symptoms consistent with infection between days 0 and 17 after the initial exposure. Overall, 5 individuals met the criteria for monkeypox testing, all of whom tested negative for infection.

Limitations of this study include potential recall bias.

According to the investigators, “Public health authorities and health care facilities should consider how these findings may inform revised estimates of exposure risk, requirements for monitoring and recommendations for PEP.

References:

Shenoy ES, Wright BS, Barbeau DN, et al. Contact tracing and exposure investigation in response to the first case of monkeypox virus infection in the United States during the 2022 global monkeypox outbreak. Ann Intern Med. Published online November 8, 2022. doi:10.7326/M22-2721