Cholera outbreaks in Africa are mainly driven by the disease spreading across countries—not because the bacteria has become more dangerous, a new study reveals.
Published in Nature Communications, the research analysed genetic information from 763 cholera samples collected in seven African countries. Scientists say this is the largest set of cholera genomes ever sequenced locally on the continent.
Using genetic tracking tools, researchers followed how different cholera strains move across borders over time. They found that the same strains repeatedly appear in neighbouring countries, showing that national borders do little to stop the disease.
“Cholera readily spreads within certain regions of Africa, indicating that cross-border transmission has a prominent role in the maintenance of cholera on the continent,” the study found.
One strain, called AFR15, was linked to some of the biggest recent outbreaks in Southern Africa, including in Malawi, Zambia, and Mozambique. The study shows this strain is still spreading and has now reached Central Africa, including the Democratic Republic of the Congo.
“We provide evidence for the rapid circulation of the AFR15 lineage associated with unusually large outbreaks in Southern Africa,” the researchers said.
Despite being linked to major outbreaks, scientists did not find evidence that AFR15 is genetically more aggressive or harder to treat than other strains. In simple terms, the scale of outbreaks is not because the bacteria has changed dramatically.
The researchers also looked at whether cholera is becoming more resistant to antibiotics. Overall, they found no major increase in drug resistance across the strains studied, which is encouraging for treatment efforts.
However, Uganda stood out as a concern, where cholera bacteria recently picked up several drug-resistance genes. This suggests resistant strains could spread across borders if not closely monitored.
The study notes that many cross-border transmissions likely go undetected due to limited disease monitoring in some areas. Stronger surveillance systems would help countries better understand how outbreaks are connected.
“Our findings emphasise the importance of regionally coordinated cross-border surveillance and interventions,” the authors said.
Photo Credit: WHO