Study finds contact tracing, exposure investigation mitigates monkeypox spread

Contact tracing and exposure investigation have helped to mitigate the spread of monkeypox virus in Massachusetts, where the first U.S. case in the current outbreak was detected, a study published in Annals of Internal Medicine found.

When this first case occurred in May, Erica S. Shenoy, MD, PhD, an associate professor at Harvard Medical School, and colleagues noted that — since monkeypox was not suspected as a cause — it presented “complexities due to multiple interactions with several health care facilities and delayed recognition of the cause, which resulted in exposures to persons in both community and health care settings.”

As part of the public and health care response, contact tracing and exposure investigation were conducted. Investigators stratified contacts based on risk, monitored contacts for symptoms, and offered and administered postexposure prophylaxis (PEP) when necessary.

Contact tracing was conducted at four Massachusetts health care facilities where the index patient was treated, while work and household contacts were identified through interviews and a review of company records. The researchers used a framework for risk assessment that was based on CDC approaches, but augmented to provide greater discrimination for exposure categories.

The CDC framework considered all health care personnel (HCP) who came into contact with the index patient while using personal protective equipment (PPE) to be low or uncertain risk. Shenoy and colleagues reported using additional details to “describe specific types of contact (both direct and indirect) separate from exposure to respiratory secretions and to stratify by PPE use.”

Contacts in all risk categories were monitored for 21 days after their last exposure.

Shenoy and colleagues identified a total of 166 contacts — 37 community contacts and 129 HCP. Among them:

• four were at high risk;
• 49 were at intermediate risk; and
• 113 were at low or uncertain risk.

No community contacts were classified as high risk.

“Three contacts with high-risk exposures and two with intermediate-risk exposures received PEP, all more than 4 days but within 9 to 13 days after exposure,” the researchers wrote.

Of the four community contacts who interacted with the index patient during the presymptomatic period, none developed monkeypox, a result “consistent with the current understanding” of virus transmission, the researchers added.

Following 21-day evaluation periods and administration of PEP, no secondary cases were identified.

Shenoy and colleagues noted that because the PEP doses were administered 4 days after exposure due to diagnosis delay, “we would not expect vaccination to prevent the development of infection, but rather to reduce the severity of illness.”

“Thus, the fact that no infection was observed among those with exposures that qualified for PEP supports the overall low risk for transmission of [monkeypox],” they wrote.

The researchers concluded that all HCP using PPE should not be considered to have sustained an exposure in the event of a monkeypox breach, and that despite the rigorous and resource-intensive process, “conducting and reporting on such investigations is critical to ensure appropriate management of exposed persons in community and health care settings and to advance our understanding of transmission risk.”

“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,” they wrote.