Dr. Cillian De Gascun:

I thank the Chairman and the members of the committee for the invitation to appear today. I wish them well with the important work they are undertaking on behalf of the Oireachtas. The invitation I received indicated that the committee wishes to focus in particular on two issues this morning: first, on the specific issue of minimising the risk of Covid-19 in the context of the phased lifting of restrictions, and second, with regard to the current understanding of the behaviour of the virus and the prospects of a second wave of the pandemic occurring. I am, of course, happy to assist committee members by answering any other queries they may have, insofar as I can.

I wish to take this opportunity to acknowledge the immense grief that many people will have experienced in recent months due to Covid-19. I wish to express my deepest condolences to all those who have lost friends and family during this pandemic.

I will first explain my own background as that may be helpful in gaining an understanding of my role in respect of the response that has been mounted to Covid-19 in Ireland. I am a medical virologist by training and have been the director of the National Virus Reference Laboratory at UCD since December 2013. It provides a clinical, diagnostic and reference virology service for hospital and community-based clinicians throughout Ireland. Indeed, it has been doing so since 1963 when it was established at the behest of the Department of Health to carry out surveillance for poliovirus following the introduction of the polio vaccine into Ireland. In that regard, the NVRL remains the World Health Organization, WHO, accredited national polio laboratory for the country. It is also the WHO national laboratory for measles and rubella and the WHO national influenza centre, contributing data annually to the global influenza surveillance and response system. In fact, Ireland was one of the founding members of the global influenza surveillance network, as it was then called, which was established in 1952. The NVRL is accredited by the Irish National Accreditation Board to ISO standard 15189. In a normal year, it performs more than 950,000 tests on more than 350,000 samples.

When SARS-CoV-2, the virus that causes Covid-19, first emerged, the NVRL was the laboratory designated to undertake testing nationally. As the pandemic progressed, the number of labs with the ability to perform testing increased, and there are now more than 40 sites at which testing is performed. With specific reference to Covid-19, I am a member of the National Public Health Emergency Team, NPHET, and chair the expert advisory group which provides technical recommendations on specific issues to NPHET and the HSE.

In the context of the current pandemic, I note that SARS-CoV-2 is a novel virus and there remains much that we simply do not know. In the first instance, we do not know the precise origin of the virus itself. SARS-CoV-2 is the seventh coronavirus known to infect humans and is a member of the sarbecovirus subgenus of the coronaviridae family. Although bats are regarded as the most likely natural host for the virus, the recombinogenic nature of coronaviruses means it can be difficult to identify the ultimate source because different parts of the genome can have different origins. This is in contrast to influenza viruses, for example, which reassort but do not typically undergo homologous recombination within ribonucleic acid, RNA, segments. As such, ascertaining the source of a novel influenza virus such as the pandemic virus of 2009 can be reduced to a question of where each of its segments originated.

We believe the likely source of SARS-CoV-2 to be bats because, following surveillance carried out after the SARS pandemic of 2003, we know there are hundreds of coronaviruses circulating in bats. In addition, the most closely related virus to SARS-CoV-2 to date is a coronavirus that was identified in a rhinolophus affinis bat sampled in the Yunnan province of China in 2013. The interesting thing about the 2013 virus is that despite being almost 96% identical to SARS-CoV-2 across the genome, the part of the genome that encodes for the protein that would allow the virus to infect humans efficiently and enter into human cells is quite different.

It is this receptor-binding domain part of SARS-CoV-2 that is, in fact, more similar to coronaviruses that have been identified in Malayan pangolins, which initially led to speculation that a pangolin could have been an intermediate host for SARS-CoV-2. However, analysis of the available sequence data suggests that the most likely divergence date of SARS-CoV-2 from its most closely related bat coronavirus ranges from 1948 to 1982. This would indicate that the SARS-CoV-2 lineage is not a recent recombinant and that, despite intensified characterisation of sarbecoviruses since SARS, viruses closely related to SARS-CoV-2 have been circulating unnoticed in horseshoe bats for many decades. The occurrence of a third significant coronavirus emergence in 17 years, together with the high prevalence of these viruses in bats that was alluded to earlier, means that these viruses are likely to cross species boundaries again.

As the committee carries out its important work on Covid-19, I ask it to do so with one eye on the future to ensure that Ireland can learn lessons from this experience and be better prepared, across all sections of society and the health service, when the next pandemic occurs. I am happy to answer any questions.