A systematic review and meta-analysis finds that colonizing strains of Staphyloccus aureus have a higher prevalence of resistance and virulence factors in low- and middle-income countries (LMICs) than in high-income countries (HICs), researchers reported yesterday in the Journal of Infection.

S aureus is known to colonize the nose and throat and can lead to a range of infections, some of which can be life-threatening, especially when the infection is caused by methicillin-resistant S aureus (MRSA). While several studies have documented the prevalence of S aureus in HICs, the prevalence of human colonization by S aureus in LMICs is not well known. 

To determine the pooled prevalence of S aureus colonization among healthy individuals in LMICs, a team led by researchers at the University of Sheffield reviewed 139 studies involving 59,732 participants in 40 countries. As secondary objective was to assess antimicrobial resistance and virulence among colonizing strains.

Global approach to surveillance needed

The pooled prevalence of S aureus at nose and/or throat was 26.4% (95% confidence interval [CI], 23.8% to 29.1%), with the highest prevalence found in South America (36.7%; 95% CI, 24.6% to 48.9%), followed by Africa (31.0%; 95% CI, 25.7% to 36.7%) and Asia (22.4%; 95% CI, 19.5% to 25.4%). By comparison, previous studies of HICs have found a pooled prevalence rate of 21.6% in European countries and 28.6% in the United States.

The pooled prevalence of MRSA in colonizing S aureus strains was 15% (95% CI, 11.8% to 18.6%), with a higher prevalence observed in Africa compared with Asia and South America (22.5% vs 13.1% vs 5.4%, respectively). Panton-Valentine leukocidin (PVL) toxin genes, which are putatively associated with virulence and transmission, were present in 26.4% of 2,531 isolates. The study authors note that studies from Europe and the United States have reported MRSA prevalence of 0% to 2% among colonizing S aureus strains, while PVL has been detected in less than 1% of European studies.

"Given the significance of S. aureus as a human pathogen, our findings underscore the need for a global approach to surveillance to effectively deploy future infection prevention strategies," they wrote.

Health officials in the Democratic Republic of the Congo (DRC) launched an mpox vaccination campaign in Kinshasa, one of the country’s hot spots, just 10 days ago, and health workers have already immunized more than 300,000 people, officials from Africa Centres for Disease Control and Prevention (Africa CDC) said today at a briefing.

Ngashi Ngongo, MD, PhD, MPH, who leads Africa CDC's mpox incident management team, said, “It’s a good testimony of the high acceptance.” He added that the DRC’s health ministry has two strategies in Kinshasa, one targeting entire populations in hot spots, and one targeting contacts of confirmed cases in other locations. The campaign includes children as young as 1-year old, and the vaccination rate has already reached 51.6% of the initial target.

More transmissible clade 1b variant detected in Kinshasa

In a worrying development, Ngongo said the recently identified clade 1a virus that has the APOBEC3 mutation, linked to more transmissibility, has been reported from Kinshasa. 

Last week, Africa CDC officials described the emergence of the new clade 1a variant. The APOBEC3 mutation had been found in the newer clade 1b virus, a change thought to contribute to its heightened transmissibility. The older clade 1a virus is thought to be more deadly and more able to cause severe disease, and officials said a more transmissible form of clade 1a raises significant public health concerns.

Overall cases in the region have gradually trended downward over the last 5 weeks, but officials have said the trend should be interpreted with caution, due to decreased and slowed testing in the eastern part of the DRC where violence is flaring, slowing testing and impacting the medical care of mpox patients.

African countries have reported 24,272 cases this year from 15 nations, and 260 people have died from their infections. Ngongo said Angola reported its first two confirmed cases from two different provinces after 8 weeks with no cases.

Ngongo said the violence in the mpox hot spot forced 605 mpox patients to flee health centers, and so far 150 people with severe infections have returned to continue their care. More than 2 million people have been displaced internally or across borders due to the violence in the eastern part of the country.

In a positive development, scaled up infection prevention and control activities consisting of training and supply procurement in the DRC has seen a 50% reduction in mpox infections in health workers, he said. In October 2023, 104 health worker infections were reported, which dropped to 52 in January 2025.