Summary
- A large outbreak of monkeypox virus clade I has been ongoing in the Democratic Republic of the Congo since 2023, causing over 20,000 cases and 1,000 deaths.
- Monkeypox virus clade I has a higher case-fatality ratio than clade IIb and is now showing signs of human-to-human transmission.
- New estimates of critical epidemiologic parameters for monkeypox virus clade I have been provided using outbreak investigation data.
- The estimated mean incubation period, serial interval, and generation time for monkeypox virus clade I have been found to be longer than for clade IIb.
- The reproduction numbers for monkeypox virus clade I are below the epidemic threshold in the Democratic Republic of the Congo, but above in the Kamituga Health Zone, indicating potential for further spread.
A significant outbreak of the monkeypox virus (MPXV) clade I is currently affecting the Democratic Republic of the Congo (DRC). With over 20,000 reported cases and 1,000 deaths, mostly among children under 15 years old, the situation is concerning. Unlike the previously known Congo-Basin clade, infections with MPXV clade I have a higher fatality rate of up to 10%. This strain is more deadly than the clade IIb, which has spread internationally mainly through sexual contact among men who have sex with men.
Evolution of Monkeypox Virus Clade I
The epidemiology of MPXV clade I is evolving, moving from a zoonotic origin to more human-to-human transmission. A new subclade has been identified in the South Kivu Province, where sexual transmission has been documented extensively. This shift raises concerns about the potential for international spread, highlighting the need to estimate critical epidemiologic parameters specific to MPXV clade I urgently.
Key Findings of the Study
A recent study used outbreak investigation data to estimate important epidemiological parameters for monitoring and modeling the spread of MPXV clade I. The study estimated the incubation period, serial interval, and generation time of the virus to better understand its transmission dynamics. The results showed that the mean incubation period of MPXV clade I was longer than that of clade IIb, with variations in serial intervals and generation times depending on the outbreak setting.
Reproduction Numbers and Transmissibility
The study also calculated the reproduction numbers for MPXV clade I, which represent the average number of secondary cases per infectious person. While the mean estimated reproduction number in the DRC was below the epidemic threshold for most of 2024, the values in the Kamituga Health Zone consistently exceeded the threshold. This higher value suggests possible viral adaptation to human transmission and increased local contact rates due to sexual transmission.
Implications and Conclusion
The findings of the study suggest a distinct timing of MPXV clade I epidemiology compared to clade IIb, emphasizing the need to investigate the role of sexual transmission and associated transmission parameters. Continued transmission of MPXV clade I in the DRC could lead to further evolution of the virus towards higher transmissibility and wider geographic spread if not controlled with contact tracing and vaccination.
In conclusion, further research is needed to improve our understanding of this emerging pathogen and its transmission dynamics. The study results provide valuable insights into the characteristics of MPXV clade I and highlight the importance of monitoring and modeling efforts to control its spread. By identifying key epidemiologic parameters and estimating reproduction numbers, researchers aim to better inform public health decisions and interventions to effectively combat the outbreak in the DRC.
Infectious Diseases, Public Health & Prevention, Epidemiology