Study finds contact tracing and exposure investigation mitigate spread of monkeypox

November 09, 2022

2 minute read


Disclosures: Shenoy reports receiving a grant from the Assistant Secretary for Preparedness and Response, the CDC and the Massachusetts Institute of Technology. Please see the study for relevant financial information from all other authors.

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Contact tracing and exposure investigation helped mitigate the spread of monkeypox virus in Massachusetts, where the first US case of the current outbreak was detected, according to 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 multiple health care settings and delayed recognition of the disease. cause, which resulted in exposures to people in both community and health care settings.

Data taken from: Shenoy E, et al. Ann Medical Intern. 2022;doi:10.7326/M22-2721

As part of the public and health care response, contact tracing and an exposure investigation were conducted. Investigators stratified contacts according to risk, monitored contacts for symptoms, and offered and administered post-exposure prophylaxis (PEP) if needed.

Contact tracing was conducted at four Massachusetts healthcare 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 risk assessment framework based on CDC approaches, but augmented to provide greater discrimination for exposure categories.

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

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

Shenoy and his colleagues identified a total of 166 contacts – 37 community contacts and 129 HCPs. 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 over 4 days but within 9-13 days of exposure,” the researchers wrote.

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

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

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

“Thus, the fact that no infections were observed among those exposed to PEP confirms the overall low risk of transmission of [monkeypox],” they wrote.

The researchers concluded that not all healthcare professionals using PPE should be considered to have experienced exposure in the event of a monkeypox breach, and that despite the rigorous and resource-intensive process, “the conduct and Reporting of such investigations is essential to ensure appropriate management of those exposed 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 results can inform revised exposure risk estimates, monitoring requirements, and recommendations for PEP,” they wrote.