Investigating MPXV Viral Clearance in Mpox Cases and Secondary Attack Rate in Contacts

Starting in late 2023, an increasing number of confirmed cases of Mpox caused by clade I Mpox virus (MPXV) were reported across several provinces of the Democratic Republic of the Congo (DRC). In August 2024, the World Health Organization (WHO) declared the ongoing outbreak a Public Health Emergency of International Concern due to its expanding geographic spread and significant public health impact.

Mpox is transmitted through direct contact with skin or mucosal lesions of infected individuals, contaminated materials. MPXV can be detected in multiple biological samples, including skin lesion swabs, blood, throat swabs, and occasionally urine. However, there is still limited information on how long and in which compartments the virus can persist, as well as on how efficiently it spreads between individuals during community outbreaks caused by clade I virus.

The MOVIE-TRACE project includes two complementary observational studies designed to address these critical gaps in knowledge and to strengthen the understanding of clade I MPXV infection in the DRC.

The MOVIE study aims to describe how MPXV is cleared from the body over time among patients with PCR-confirmed Mpox infection. Despite the importance of isolation and infection control in outbreak management, there is limited evidence on how long individuals remain infectious. MOVIE addresses this critical gap by conducting longitudinal follow-up of Mpox-positive patients for up to two months, with several scheduled visits during which multiple biological specimens are collected. These samples will be analyzed to assess viral persistence in different body compartments and to characterize the kinetics of viral clearance. The findings will help refine isolation duration, improve clinical management, and guide infection prevention policies.

The TRACE study seeks to understand how Mpox spreads from confirmed cases to their contacts. By systematically collecting exposure data and testing contacts for infection, TRACE will estimate the Secondary Attack Rate (SAR) and identify factors that increase the likelihood of transmission. This information will support public health measures such as contact tracing, quarantine strategies, and targeted vaccination in endemic regions.

Together, MOVIE and TRACE will generate essential evidence on both viral clearance and transmission of clade I MPXV, providing a comprehensive understanding of the infection and informing data-driven outbreak response strategies in the Democratic Republic of the Congo.

Inclusion criteria

• MOVIE Study:

• Individuals of any sex and age presenting with lesions clinically suggestive of Mpox, as assessed by a trained health worker.
• Symptom onset within the 10 days prior to the baseline assessment.
• Willingness and ability to comply with study procedures and attend scheduled follow-up visits for up to two months.
• Availability for follow-up throughout the study period.
• Provision of written informed consent by the participant, or consent by a legally authorized representative for minors or individuals unable to provide it themselves.
• Assent obtained from children aged 12 years or older.
• For participants who cannot read or write, witnessed consent will be obtained.
• TRACE Study:

• Individuals who have had close physical contact with a polymerase chain reaction (PCR)-confirmed Mpox case within 14 days from the onset of symptoms in the index case.
• Close physical contact is defined as being within 2 meters of an infected person-particularly in enclosed spaces-for at least 5 minutes (based on CDC's 2-meter rule for droplet transmission).
• Willingness and ability to comply with the study protocol and attend scheduled follow-up assessments.
• Provision of written informed consent by the participant, or consent by a legally authorized representative for individuals unable to provide it themselves.

Exclusion criteria

• MOVIE Study:

• Cases of severe Mpox requiring hospitalization.
• Individuals with a confirmed alternative diagnosis explaining their illness.
• Prior vaccination against Mpox.
• Individuals over 40 years of age who report having received smallpox vaccination during infancy.
• TRACE Study:

• Prior vaccination against Mpox.
• Individuals over 40 years of age who report having received smallpox vaccination during infancy.