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

Background: In May 2022, the first case of monkeypox virus (MPXV) infection in the United States in the current global outbreak was identified. As part of the public health and health care facility response, a contact tracing and exposure investigation was done. Objective: To describe the contact tracing, exposure identification, risk stratification, administration of postexposure prophylaxis (PEP), and exposure period monitoring for contacts of the index patient, including evaluation of persons who developed symptoms possibly consistent with MPXV infection. Design: Contact tracing and exposure investigation. Setting: Multiple health care facilities and community settings in Massachusetts. Participants: Persons identified as contacts of the index patient. Intervention: Contact notification, risk stratification, and symptom monitoring; PEP administration in a subset of contacts. Measurements: Epidemiologic and clinical data collected through standard surveillance procedures at each facility and then aggregated and analyzed. Results: There were 37 community and 129 health care contacts identified, with 4 at high risk, 49 at intermediate risk, and 113 at low or uncertain risk. Fifteen health care contacts developed symptoms during the monitoring period. Three met criteria for MPXV testing, with negative results. Two community contacts developed symptoms. Neither met criteria for MPXV testing, and neither showed disease progression consistent with monkeypox. Among 4 persons with high-risk exposures offered PEP, 3 elected to receive PEP. Among 10 HCP with intermediate-risk exposures for which PEP was offered as part of informed clinical decision making, 2 elected to receive PEP. No transmissions were identified at the conclusion of the 21-day monitoring period, despite the delay in recognition of monkeypox in the index patient. Limitation: Descriptions of exposures are subject to recall bias, which affects risk stratification. Conclusion: In a contact tracing investigation involving 166 community and health care contacts of a patient with monkeypox, no secondary cases were identified.