There had been anecdotal evidence here and there after previous Ebola outbreaks, but the number of survivors was not high and rigorous follow-up studies were lacking. The magnitude of the West African oubreak, however, has brought the issue of long-term, Ebola-virus-induced sequelae to the forefront, as over 17,000 people have survived the infection. The results of an initial follow-up of 82 Liberian survivors, presented at the annual meeting of the Academy of Neurology and reported by BBC news, show widespread serious problems, ranging from weakness, memory loss and depression, to two patients being actively suicidal. This is an initial report of a much larger study of long-term health problems after Ebola virus infection.

Whether ongoing viral replication, latency in reservoirs or the immune response to infection are the underlying cause of some of these problems remains to be determined. Probably all of these factors, and perhaps others, are involved to varying extents. Of note, Ebola virus has been detected in spinal fluid of patients, including the previous hospitalization of the Scottish nurse that has just been readmitted to the hospital for the third time after initially recovering from infection. In the study follow-up study mentioned above, 38% of men had tested positive for Ebola in their semen at least once within the year after recovering, and in one case 18 month after recovery. Nevertheless, most survivors said they were sexually active and only 4% used profilaxis, which suggests that continued flare-ups are to be expected, given that sexual transmission has been documented.

This is a crucial study, and many of this type will be needed if we are to understand the long-term consequences of Ebola infection -might an acute viral disease need to be considered chronic in a significant number of cases?