It is not exactly breaking news that the Ebola virus may persist in some organs and bodily fluids (i.e. semen, breast milk, etc.) for months (see ECDC On Ebola Persistence & Rapid Risk Assessment) after victims recover. Nor is the potential for sexual transmission, or transmission via breast feeding.
A year ago, in MMWR & WHO On Risks Of Sexual Transmission Of Ebola we looked at a suspected case of sexual transmission in March of 2015 from a male patient who had been believed `recovered’ for well over six months.
And last February the WHO issued interim guidance on Clinical care for survivors of Ebola virus disease which advised nursing mothers to have their breast milk tested.
Due to the possible risk of virus persistence in breast milk, EVD survivors who are lactating are encouraged to have their breast milk tested for Ebola virus by RT-PCR. Women who do not know the status of their breast milk or who were tested and for whom no Ebola virus RNA was detected should continue breastfeeding. If Ebola virus RNA is detected, breastfeeding should be suspended and the breast milk retested every 48 hours until two consecutive “undetected” results are obtained
Today, however, we have a study - published in the journal Virus Evolution - that used genetic sequencing to identify the lineage of Ebola infections during the tail end of the outbreak in Sierra Leone, and which indicates sexual or breast milk transmission was likely in a handful of cases.
The study - in the form of a preliminary PDF - is available at:
Rapid outbreak sequencing of Ebola virus in Sierra Leone identifies transmission chains linked to sporadic cases
Given the formatting challenges we'll skip directly to the press release from Wellcome Trust, one of the sponsors of this study, which provides some background and details on their findings. Follow the link to read it in it's entirety.
An international team of researchers has produced a detailed picture of the latter stages of the outbreak in Sierra Leone, using real-time sequencing of Ebola virus genomes carried out in a temporary laboratory in the country.
While the study did not suggest that unconventional transmission was more common than previously thought, the authors describe several instances including a mother who may have transmitted Ebola to her baby via breastfeeding, and an Ebola survivor who passed on the virus sexually a month after being released from quarantine. [More details of cases in the notes to editors].
The research, published today in the journal Virus Evolution, suggests that rapid sequencing of viral genomes in the midst of an epidemic could play a vital role in bringing future outbreaks under control, by allowing public health workers to quickly trace new cases back to their source.
Starting in mid-2015 samples from all new Sierra Leone cases were rapidly sequenced in the facility. The data, combined with the growing reference set, helped field workers locate the source of infection for some of the final Ebola cases in Sierra Leone. This work revealed that some cases were acquired through unconventional transmission chains and supports a growing body of evidence that the Ebola virus can be found in fluids such as semen or breast milk and may persist beyond the standard quarantine times.