Friday, July 10, 2015

WHO: Genetic Sequencing Of New Liberian Ebola Cases





The sudden reappearance of Ebola in Liberia after more than 3 months raised a lot of questions and sparked a number of theories as to how it might have returned.  Among them, the index case might have had contact with someone with recent travel to Guinea or Sierra Leone, or that he might have contracted the virus from a zoonotic source (bat, bushmeat, etc.).

To try to unravel this mystery, samples of the virus were sent to the Liberian National Reference Laboratory for genetic sequencing. The result?  The virus is genetically similar to viruses sequenced from the same county six months ago.


While the results don’t tell us exactly how this first case in three months became infected, they do seem to exclude a new zoonotic jump or importation from Sierra Leone or Guinea. 


That pretty much leaves us with a local as-yet unknown source of infection. Possibly from someone who recovered from the virus, but is still unknowingly shedding the virus (see MMWR & WHO On Risks Of Sexual Transmission Of Ebola).  

We continue to see a significant number of cases still occurring in Sierra Leone and Guinea where the chain of infection remains unknown, and/or the diagnosis was only made post-mortem. 


Both of which illustrate how difficult getting to zero really is going to be in this Ebola outbreak.



Liberia update: New information from genetic sequencing

Ebola situation assessment
10 July 2015

On 29 June 2015, a new case of Ebola virus disease was identified in Liberia 50 days after interruption of active transmission was achieved on 9 May. Since then, a cluster of cases has been identified, all of them from Nedowein in Margibi county. Currently, 5 people have been confirmed with Ebola virus disease by laboratory testing.

As part of the investigation into the source of this new cluster of infections, samples taken from the first person found to have Ebola were sent to the Liberian National Reference Laboratory for genetic sequencing. Tests on these samples have shown that the virus is genetically similar to viruses that infected many people in Margibi County more than 6 months ago, in late 2014.

This information provides important insights into the probable origin of the virus responsible for this new flare in Liberia. Because the virus appears to be related to the one previously circulating in Liberia, it is unlikely that this recurrence has been caused by virus imported from infected areas of Guinea or Sierra Leone. It also makes it unlikely that this has been caused by a new emergence from a natural reservoir, such as a bat or other animal.

Genetic sequencing on samples from the 4 other cases in this new outbreak is underway.

149 contacts currently being followed

Presently, 149 people have been identified as contacts and are being monitored closely. Four of these people have tested positive and are being treated for Ebola virus disease in Ebola treatment centres. As with all cases, the number of contacts has been fluctuating. Some are true contacts, while others are not. When a suspected case is confirmed as negative, all contacts associated with that case are de-listed, which is why the number of contacts has declined this week.

Detailed clinical, epidemiological and laboratory investigations are on-going to identify the initial source of infection. This includes the genetic sequencing that has suggested this virus is linked to virus circulating in earlier chains of transmission in Liberia.

At the time of the diagnosis of the first case of the new cluster, Liberia was mid-way through a 90-day period of heightened surveillance and vigilance, following the completion of 42 days since the burial of the last person infected with Ebola virus disease and the declaration of the interruption of transmission in Liberia. During this period, anyone meeting the clinical criteria for Ebola virus disease has been tested and post-mortem tests for Ebola virus are regularly conducted. The new case of Ebola was detected as a result of the heightened surveillance measures being implemented during this period.

Liberia and international community work together to manage the outbreak

Liberia has undertaken the relevant planning to prepare for and respond to the recurrence of Ebola. The Incident Management System immediately activated a team to carry out a detailed investigation and began tracing people who had been in contact with the young man while he was symptomatic.

The UN system and non-governmental organizations (NGOs) are supporting the Government with staff already in Liberia. WHO has sent additional experts in epidemiology and social mobilization to ensure that the processes needed to stop transmission are in place and that the community is fully involved in identifying contacts. WHO has staff present in all 15 counties of Liberia and is playing a central role in supporting the Government’s efforts to strengthen surveillance across the country.

Other UN agencies and partners are assisting households being kept in quarantine. The World Food Programme is providing food, UNDP is providing solar lamps and radios and UNICEF is supplying mattresses and tents to provide families with more space.

The identification of Ebola virus disease and quick activation of a comprehensive, multi-sectoral, inter-agency response shows that capacity exists to quickly identify, track and monitor contacts – one of the core elements of the strategy for stopping further spread of Ebola disease.

The Government is keeping the people of Liberia informed of developments and is reinforcing messages on key steps they should take to protect themselves and their communities. WHO and partners are fully committed to assisting the Government and communities to end this recurrence of Ebola as rapidly as possible

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