Just how little we actually know about Ebola virus disease became apparent in the last 48 hours.
First, doctors are shocked by the late recurrence of the infection and rapid deterioration in a Scottish nurse. Secondly, the results of a preliminary study on Ebola virus persistence in male survivors in Sierra Leone were surprising.
Pauline Cafferky survived a serious bout of haemorrhagic fever, which she contracted late last year while nursing children with Ebola in Sierra Leone.
Anecdotally, public health workers in west Africa report post-Ebola symptoms, including joint pain in the lower back and hips, forgetfulness and skin rashes. However, there are no reports so far of anyone in Africa suffering a severe recurrence of infection in the way Cafferky has.
The study, published online by The New England Journal of Medicine, found that one quarter of men tested some seven to nine months after they were first infected had Ebola virus present in their semen. It had been thought that Ebola remained in semen for up to four months after acute infection.
All 93 men will now be retested at intervals in an attempt to discover what factors may be associated with the persistence of the virus.
No risk factors
In March 2015, Ebola virus disease (EVD) developed in a Liberian woman after the country had been free from EVD for 30 days.This woman had no identifiable risk factors for EVD other than sexual contact with a male survivor of the disease. This survivor’s semen tested positive for Ebola virus genetic material, which indicated sexual transmission occurred some six months after he was first infected.
The case is only the second ever recorded of sexual transmission of a filovirus, the group of viruses to which Ebola belongs, suggesting it is a rare event.
That Ebola virus can persist in various sites in the body for months does not come as a surprise. Such sites include the placenta, breast milk and the central nervous system, as well as semen.
Persistence of other viruses such as Hepatitis C in the human body is well established.
How worrying are the latest discoveries concerning Ebola? In terms of infectivity, the indications are that Cafferky does not have symptoms, such as bleeding and vomiting, that would make her a significant infection risk.
For the 8,000 or so African men who survived initial infection, they face the prospect of sexually transmitting the disease to their partners up to nine months after recovery.
This has public health implications for health systems in Guinea, Liberia and Sierra Leone, which have already been stretched beyond limits in the past 18 months.