The Ro figure quoted is - as acknowledged - very much higher than recent estimates of 1.5-2.0. An interesting comparison could be made with the arrival in Dallas of an asymptomatic individual who became symptomatic, presented at hospital, returned to the community and was only admitted three days later. Considering the time that has subsequently elapsed it appears clear that there were only two nosocomial transmissions in this instance. There may be differences in clinical presentation which account for the markedly different outcomes of these two introductions. Nevertheless, I think this deserves comment. It is estimated that there will be ~3 asymptomatic exports from West Africa a month and the range of potential secondary cases is therefore of significant concern to the countries that will import them.