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Blog Virology

Ebola Strikes Again in the DRC

A second simultaneous Ebola outbreak has been confirmed in the Democratic Republic of Congo (DRC), (World Health Organization, 2020). This marks the 11th Ebola outbreak in central Africa which comes at a time when the continent also battles the COVID-19 pandemic.

First discovered in 1976, ebola viruses have since re-emerged across the African continent. The virus reached international attention during the longest and most extensive Ebola outbreak in West Africa between 2013 – 2015.

Historical Ebola outbreaks have fatality rates as high as 88%, almost 9 out of 10 people would die as a result of infection. The West Africa outbreak, however, saw a drastic reduction in fatality rate, to around 40%. The reduction in fatality rate was likely a result of the increased basic support, advanced and more appropriate care for those infected and earlier case detection, allowing for better management of both patients and outbreak spread (Baseler et al., 2017).

The most recent outbreak is in Mbandaka in the Équateur region, 600 miles from the ongoing Kivu Ebola epidemic in the North Kivu and Ituri provinces. The cases in Mbandaka are thought to be separate from the Kivu Ebola epidemic and instead the result of a new ‘spillover’ event from an animal reservoir to humans.

As of the 10th of June, a total of 12 cases have been reported; 9 confirmed cases, 3 suspected cases and 6 deaths, (Bujakera, Holland and Heavens, 2020)*. Positive samples were confirmed via testing at the Institut National de Recherche Biomédicale (INRB) – the countries national medical research organisation.

Although case number is relatively small at present, this is likely to rise as contacts are traced and the incubation period of 2-21 days elapses. Whilst the outbreak has presented at an already challenging time, scientists and doctors are on the ground with capacity to trace and diagnose. This service was expanded and refined in 2018 in response to previous outbreaks (World Health Organization, 2020).

The Kivu Ebola epidemic began in August 2018, over 3,400 people have been infected and sadly 2,200 lives lost despite the implementation of aggressive control measures. A number of factors have hindered this operation including; stigmatization, civil unrest and logistical issues.

Community level prevention and outbreak measures are dependent on the public trusting local authorities, however 31.9% of 961 individuals surveyed in North Kivu trusted that local authorities were acting in their best interests. The same survey reported 25.5 % of those surveyed believed the outbreak was a hoax, (Vinck et al., 2019). Complicating this were populist politicians publishing their own doubts on the outbreak validity to gain support in the 2018 elections. The country had not yet had a peaceful transition of power since decolonialisation in 1960, (Moran, 2018).

However, deployment of an experimental vaccine, coupled with rapid diagnostics helped to halt the outbreak. Following emergency use in 2016, the Ervebo vaccine was finally approved for use in 2019, after clinical trial demonstrated safety and efficacy; 97.5% efficacy in preventing Ebola infection compared to no vaccination, (Regules et al., 2015; World Health Organization, 2019).

Although an effective vaccination is now available, this is by no means the end of the problem. Availability, difficulties in contact tracing and public perception are all challenges that must be addressed to manage the outbreak during an already arduous time.

It is hoped that authorities and individuals alike can action their learnings from previous outbreaks, to bring this new outbreak to a swift end.

The DRC is currently contending with outbreaks of cholera, SARS-CoV-2, measles and two separate Ebola clusters. This serves as a stark reminder that whilst the world fights against the SARS-CoV-2 pandemic, Ebola outbreaks will stop for no country and no person.

Viruses emerge, or spillover often in nature, ebola virus is an example of this. Check out our blog on viral emergence here, or our post about bats and viruses.

*Please note that this article is not by a scientific body and reports figures from a WHO press conference which could not be confirmed on WHO.int.

Written by Charlotte Rigby

Citations

Baseler, L. et al. (2017) ‘The Pathogenesis of Ebola Virus Disease’, Annual Review of Pathology: Mechanisms of Disease, 12(1), pp. 387–418. doi: 10.1146/annurev-pathol-052016-100506.

Bujakera, S., Holland, H. H. and Heavens, A. (2020) Up to 12 infected in Congo’s new Ebola outbreak: WHO, Reuters.

Moran, B. (2018) ‘Fighting Ebola in conflict in the DR Congo’, The Lancet. Elsevier, 392(10155), pp. 1295–1296. doi: 10.1016/S0140-6736(18)32512-1.

Regules, J. A. et al. (2015) ‘A Recombinant Vesicular Stomatitis Virus Ebola Vaccine’, New England Journal of Medicine. Massachusetts Medical Society, 376(4), pp. 330–341. doi: 10.1056/NEJMoa1414216.

Vinck, P. et al. (2019) ‘Institutional trust and misinformation in the response to the 2018–19 Ebola outbreak in North Kivu, DR Congo: a population-based survey’, The Lancet Infectious Diseases, 19(5), pp. 529–536. doi: https://doi.org/10.1016/S1473-3099(19)30063-5.

World Health Organization (2019) Preliminary results on the efficacy of rVSV-ZEBOV-GP Ebola vaccine using the ring vaccination strategy in the control of an Ebola outbreak in the Democratic Republic of the Congo: an example of integration of research into epidemic response. doi: 10.1016/j.surfcoat.2019.125084.

World Health Organization (2020) New Ebola outbreak detected in northwest Democratic Republic of the Congo; WHO surge team supporting the response. Available at: https://www.who.int/news-room/detail/01-06-2020-new-ebola-outbreak-detected-in-northwest-democratic-republic-of-the-congo-who-surge-team-supporting-the-response (Accessed: 2 June 2020).

Blog Virology

Bats and Viruses

The 17th of April marks International Bat Appreciation Day. This is because bats begin to emerge from hibernation at this time of year. Despite all the bad press bats get, especially in light of the coronavirus outbreak, they actually play an important roll in nature.

Bats are insectivorous creatures, and reduce the number of many annoying insects. Did you know a bat can eat up to 1000 mosquitoes in an hour?!

Bats are fascinating mammals. Unique in several ways, including their ability to fly, they also have a harmonious relationship with many viruses that can be devastating to humans. 

https://images.theconversation.com/files/313184/original/file-20200202-41495-ndlo4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1200&h=1200.0&fit=crop

Viruses such as Ebola virus, Coronaviruses (e.g. SARS), and Hendra virus are examples of Zoonotic viruses that are found in bats. Zoonotic is the term for viruses that jump species barriers or “spill over”, i.e. from bats to humans. These viruses often cause no physical symptoms in bats, and due to their lifestyle of roosting in large colonies, can spread easily through large populations. 

Wynee and Wang (2013) from CSIRO Australian Animal Health Laboratory, Geelong, Australia, released an open-access article in PNAS asking whether bats are friends or foe. They remind us that bats are just as diverse as the viruses that infect them. The picture below, also found in their article shows different species of bats, and electron microscope images of the viruses that can infect them (1).

“Bats are diverse, as are the viruses that infect them.

The Chinese horseshoe bat (ARhinolophus sinicus) is one of many Rhinolophus sp. that are a natural host of SARS-like coronaviruses (B; scale bar 100 nm). The spectacled flying fox (CPteropus conspicillatus) along with other Pteropus sp. are reservoirs for the Australian Bat lyssavirus (D; scale bar 100 nm). A number of African fruit bats including Hypsignathus monstrosus (E) have been found to host Ebola virus (F; Ebola Reston, scale bar 200 nm). The Malayan flying fox (GPteropus vampyrus) is the natural host of Nipah virus (H; scale bar 200 nm). All four pteropid Australian bat species including Pteropus alecto (I) have been found to carry Hendra virus (J; scale bar 200 nm).”

https://doi.org/10.1371/journal.ppat.1003651.g001

The reasons for why bats can tolerate these viruses are not fully understood, but there are some characterised differences in their immune system response that are thought to account for this (2)

One relatively well supported hypothesis for the underlying reason is due to their flight, which puts a large amount of stress on the body. Evidence suggests that they have managed to deal with this stress by the evolution of an altered immune response, which then allows the bats to control viral replication whilst minimising any counter-productive over response (3)

All of this is great for bats, but becomes a problem for us when these viruses jump into the human population. Our immune systems respond differently to bats, and this results in the diseases we see. So, what can we do?  

To some, the obvious response may be to exterminate wild bat populations. Even without considering the obvious moral objections to this, it would also be counter-productive for many reasons. Bats are incredibly important to ecosystems, playing crucial roles in pollination, insect control, and seed dispersal (4)

In order to reduce the chances of spill over events, it is important to look at the ways that human activity brings us into more frequent contact with bats, such as deforestation and the possibility of bats passing diseases to us via animals in our food supply chains. We can then find ways to minimise these.  

In the meantime, researchers can learn a lot from the differences between the immune system response of humans and bats, in order to identify ways in which ours is not effective in tackling viruses. (2)

We should appreciate these wonderful mammals, understand the ways they can be dangerous, and learn to live alongside them whilst minimising contact. It will suit both us and them!  

https://i.pinimg.com/originals/b2/e3/98/b2e3989557c230febf0b46c69c0969ab.jpg

References: 

1: Bats and Viruses: Friend or Foe? – Wynne & Wang, 2013

2: Innate Immune Responses of Bat and Human Cells to Filoviruses: Commonalities and Distinctions – Kuzmin et al, 2017 

3: Novel Insights Into Immune Systems of Bats – Banerjee et al, 2020 

4: Education to Action: Improving Public Perception of Bats – Hoffmaster et al, 2016 

Written by Ben Jones
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