Health officials in Equatorial Guinea have confirmed four cases in Bata, which has a busy deep water port and an international airport flying to neighbouring Cameroon and Gabon.
In all, cases have been recorded in three provinces across a 90-mile range, and officials admit they have been unable to establish links between all the infections.
Moritz Kraemer, associate professor of computational and genomic epidemiology at Oxford, said: “The spread of Marburg virus to the port city Bata is concerning. When new outbreaks spread into larger and more connected cities the risk of regional spread increases.
“There have now been reports of confirmed and probable cases across multiple cities and districts in Equatorial Guinea and it’s not unlikely that the extent of the outbreak is larger than currently reported. Enhanced contact tracing will help identify chains of transmission.”
Dr Michael Head, senior research fellow in global health at the University of Southampton, said: “Whilst we wouldn’t anticipate any Covid-like global spread from the current outbreak, it’s entirely possible we could see a scenario similar to the spread of Ebola across West Africa in 2014-15.
“It’s hard to tell from the outside, looking in, as to whether there is anything more that could or should have been done. However, the spread to a capital city is a concerning aspect. We don’t know for sure what will happen next, but the spread of the disease with so many cases across a wide geographical area indicates the outbreak will continue for some time to come yet.”
Little official information has emerged from the country since the outbreak was confirmed in February. An update last week disclosed there had been nine laboratory confirmed cases. Seven of those have died. There have also been 20 further suspected cases, all of whom have died.
The WHO on Thursday said it was aware of additional cases and urged the government to report them.