Experts are questioning what has caused the large increase in meningitis cases compared to previous epidemics. Emma Wall, a clinical professor of infectious diseases at Queen Mary University of London, described this question as the most fascinating one arising from the current epidemic. An outbreak of meningitis A in the Sahel, an area from Senegal to Sudan and Eritrea, involved thousands of cases. The MenB strain has never before caused an outbreak of this magnitude. In the UK, outbreaks of MenB have previously been small, such as two cases of MenB 20231 or cases over many years in Gloucestershire in the 1980s. Wall said she is investigating whether the strain has acquired the ability to spread faster.