An mpox antibody test built during the Rwandan outbreak it was designed to fight

Most diagnostic tests arrive after an outbreak peaks. This one was built inside the wave.

During the mpox clade 1b outbreak in Rwanda, a team from the University of Birmingham, the Rwanda Biomedical Centre (RBC), and the University of Rwanda developed and validated an IgG ELISA assay for mpox antibodies directly at the National Reference Laboratory in Kigali. The test, described in The Lancet Infectious Diseases, represents the first time an antibody assay for mpox has been validated within an active outbreak of the newer clade 1b strain.

Four signatures, designed for resource constraints

The MpoxCARE project, as the initiative is called, deliberately designed the test around just four key antibody signatures. The reasoning was practical: a test that requires dozens of reagents or expensive equipment will not work in remote laboratories across East Africa, where mpox is spreading and where the need for serosurveys is most urgent.

The assay detects IgG antibodies to mpox virus that appear after either natural infection or vaccination. This dual capability is important. Public health authorities need to know not just who has been infected, but who has developed immunity through vaccination, in order to make informed decisions about where to direct limited vaccine supplies.

Validation involved blood samples from three clearly defined groups in Rwanda: individuals who had received an mpox vaccine, people with confirmed prior mpox infection, and unexposed controls with no disease history or vaccination. The test was assessed on its ability to correctly identify which participants had developed mpox-specific antibodies.

Dried blood spots extend the reach

One of the more practical features of the assay is its compatibility with dried blood spots (DBS), not just venous serum. In settings where trained phlebotomists and cold-chain storage are scarce, DBS collection is far simpler. A finger prick on filter paper can be stored at room temperature and transported without refrigeration. This extends the test's geographic reach considerably, potentially enabling serosurveys in rural communities that lack the infrastructure for conventional blood draws.

What the test enables

An antibody test does not diagnose active infection. That is the job of PCR and antigen tests. What an antibody test does is map the immunological landscape of a population: who has been exposed, who is protected, and who remains vulnerable. This information feeds directly into outbreak management decisions.

For mpox specifically, knowing the extent of population immunity helps answer several pressing questions. Are transmission chains being driven by fully susceptible individuals, or are reinfections occurring? Is the vaccine producing durable immune responses in the populations receiving it? How does immunity wane over time? Without a validated antibody test, these questions cannot be answered with any precision.

Partnership as method

The project reflects a longstanding research partnership between Birmingham and the RBC that emphasizes capacity building alongside scientific output. The collaboration includes international PhD studentships and infectious disease research expertise drawn from the UK's National Health Service and National Institute for Health Research. The test was explicitly designed to be validated in the population and setting where it would be used, rather than developed elsewhere and deployed after the fact.

Limitations and next steps

The published validation was conducted at a single laboratory site in Kigali. Multi-site validation across different laboratory environments and operator skill levels would strengthen confidence in the test's reproducibility. The sample sizes for each validation group were not reported in the press materials, and independent assessment of sensitivity and specificity across larger cohorts will be important.

The test detects antibodies to orthopoxviruses broadly, and distinguishing mpox-specific immunity from cross-reactive responses to related viruses, including vaccinia from smallpox vaccination, requires careful interpretation. The four-antigen design was chosen to balance specificity and feasibility, but its performance in populations with mixed exposure histories needs further characterization.

Longitudinal studies tracking antibody levels over months and years will be needed to understand how immunity evolves post-infection and post-vaccination, information that is critical for setting revaccination schedules and predicting future outbreak susceptibility.

The test is now available as part of the public health toolkit for mpox surveillance in East Africa. Whether it arrives in time to shape the current outbreak's trajectory depends on how quickly it can be deployed beyond Kigali.