Results of an international study suggest France and the UK experience the highest number of malaria cases imported from other countries.
Researchers mapped the movement of malaria from endemic countries to 40 countries defined as being malaria-free.
The countries with the highest average number of imported infections per year over the past decade were France (2169), the UK (1898), the US (1511), Italy (637), and Germany (401).
Infection movement was strongly skewed to a small number of “high-traffic” routes, with malaria cases originating from West Africa accounting for 56% (13,947) of all cases detected in non-endemic countries.
These results were published in The Lancet Infectious Diseases.
“This is the first world-wide assessment of imported malaria cases in 20 years, and mapping this data is hugely valuable in helping us understand how we can mitigate against the effects of the global movements of the disease,” said study author Andrew Tatem, PhD, of the University of Southampton in the UK.
“Imported malaria can be expensive to treat, contribute to drug resistance, sometimes cause secondary local transmission, and threaten the long-term goal of eradication. This study forms part of wider efforts to understand patterns of human and malaria parasite movement to help guide elimination strategies.”
For this study, researchers analyzed a database of nationally reported statistics on imported malaria covering more than 50,000 individual cases over 10 years.
Although most incidents of malaria in non-endemic countries originated in West Africa, the study showed that 20% were from India (4988), 13% were from East Africa (3242), and 3% were from Papua New Guinea (748).
And although the routes from West Africa to France and the UK showed the strongest imported malaria link, there were other high-traffic routes. These included India to the US (149 cases on average per year), Papua New Guinea to Australia (97), Pakistan to the UK (69), and Haiti to the US (52).
By mapping this network of malaria movements across continents, the researchers showed that a number of factors, beyond geographic ones, may influence the strength of importation levels.
For example, the researchers believe that historical, economic, language, and cultural ties all play a part. They said population movements with former colonies had particular influence; such as Nigeria, Ghana, and Kenya with the UK, and Mali, Niger, and Chad with France.
The researchers hope to conduct further studies to examine which factors are the drivers behind the patterns of malaria spread between endemic and non-endemic countries.
