A One Health Perspective on Disease Dynamics: Human Monkeypox Transmission in Sankuru District, Democratic Republic of Congo

Background: Reports from the first monkeypox (MPX) active surveillance program in the Democratic Republic of Congo (DRC) in the 1980s determined that the disease was not of epidemic potential, with R0<1. However, during an active surveillance period from 2005-2007, researchers found a 20-fold increase during the last 30 years. The purpose of this study was to analyze the contact data from 2005-07 and compare characteristics to those of the 1980s, and toassess the change in R0 of MPX. Methods: Contact tracing information and samples from active lesions were collected. Samples were screened by PCR and positive cases were ranked by generation and grouped into chains of transmission according to date of rash onset, contact tracing, and location. R0 was determined using calculations provided in the 1980s study and chain size distribution was compared. Results: Of 1407 suspected cases of MPX investigated in 2005-07, 287 provided contact information with an average of 6.22 (range, 1-20) contacts each. Among the 703 positive cases, 408 distinct chains of transmission were identified. Average chain size was 1.75 cases (range, 1-12), with the longest reaching six generations. The crude secondary attack rate (AR) was 0.092, with an effective R0 of 0.576. Discussion: Contact characteristics and types of contacts differed from those of the 1980s program. This analysis found a higher crude secondary attack rate and effective R0. This could be the result of a higher proportion of unvaccinated contacts, or that the virus is better able to transmit between humans with a more limited amount of contact.