We must co-ordinate Northern and Southern responses to Covid-19…

To quote W.Edwards deming “In God we trust, all others bring data”.

When I wrote my first article for slugger in February, I did an overview of Covid 19 and how epidemiologically it may be difficult trying to manage an outbreak on an island with two different approaches. This review will review the current public health approaches to managing Covid. There is a lot more evidence about what works, what doesn’t work, and what may work. Epidemiology is a science based on common sense and the general public understand the principals involved.

The virus spread more widely and quickly in Europe and US. It is hard to imagine that any government would have planned to let the virus go out of control to protect the economy and then to do a massive lockdown 2 weeks later to reduce loss of life.  Unlike countries such as Singapore, South Korea, China, most European countries had an abysmal first response trying to contain this virus. They did this because too many scientists and policy makers made too many assumptions about the virus. This has been one of the fundamental problems with Covid management. Policies are always trying to catchup with a virus that moves exponentially.

The Covid virus had several properties making it difficult to contain from the start. It was easily transmitted. However, probably the most crucial factor in this outbreak has been the asymptomatic or minimal symptoms experienced by a significant proportion of people. Follow that with a 5-day incubation period, another 5 days of mostly minor illness before people get sick and seek hospital care, exponential growth, the surge arrives unless there are active surveillance and containment strategies in the community.

People can have high levels of virus in their respiratory secretions when they do not have symptoms, and talking is enough to produce droplets.  Yet until social distancing health policies were introduced, containment strategies were based on symptoms or travel history. The only other policy aimed at trying to reduce the introduction of infection from asymptomatic people was the quarantine of people who were re-patriated to the UK from Wuhan. Testing strategies have failed; the evidence for this is the unfolding human disaster in hospitals across Europe.

NI introduced major social distancing with incremental changes starting on 16 March. This is to flatten the curve. There is another epidemiological concept called the basic reproduction number Ro. Ro is the number of secondary infections generated by a single case. For Covid  19 it varies between approximately 2.5-3.5. That means on average one infected person tends to infect between 2.5 and 3.5 other people. Social distancing is our attempt to reduce Ro.

However the benefits of the current massive social distancing will be lost if we do not add in other components to try to bring Ro<1.  In an outbreak if you get Ro to less than one, ie every infection causes less than one new infection, the outbreak burns out. As long as infections are not introduced from outside, and Ro< 1 can be sustained over time, the outbreak will be over. As a vaccine seems quite distant, trying to reduce Ro < 1 is our only tool.

The Republic of Ireland introduced social distancing 4 days before UK, and thereafter there were some minor difference in policy between the two jurisdictions but the social distancing policies have converged. Whether people exercise more or less than 2 km from their house is probably not a major policy difference. However, there is a major fundamental separation in the additional policies trying to reduce Ro<1. The Republic of Ireland is trying to find cases, test more extensively, isolate contacts, and stop transmission chains. UK/NI seems to have given up on any community testing and is only testing people in hospital. There is advice to self-isolate if symptoms of a cough, etc., but there is already proof that asymptomatic people could be infectious.

The social distancing policies are very disruptive to people’s lives, and are detrimental to the economy. The additional testing and case finding would augment social distancing and would allow more control of the community transmission and allow earlier relaxation of some of the social distancing policies. Trying to find contacts and cut down transmission chains is easier when people are social distancing and contacts are fewer and more memorable. I can remember all my contacts in the last 7 days, which is unusual, but this is an added benefit of social distancing.

We know that the widespread testing policies, isolation of cases, and tracing contacts works, as we have proof from China, Singapore and South Korea and decades of applying this concept to other outbreaks.

One of the most important lessons in managing this pandemic is the need to be agile, and understand local epidemiology and develop strategies that are responsive to the local outbreak.  If the basic principle that the most cautious approach based on current evidence is used, then we may be able to catch up with the virus instead of running faster and faster and finding it hard to catch up.

There is a big argument for trying to contain an outbreak within a country. Less affected areas will then be in a better position to provide ventilators, PPE, healthcare workers to help the affected city. China was a good example of that when it shut down Wuhan, and then pulled in resource from less affected areas of China.

We have no concrete evidence that herd immunity will work long-term, it might and I hope it does, but no proof, and certainly not enough evidence to form a basis for a large-scale public health policy. Many infections provide immunity once infected eg measles. Some infections do not provide any immunity or it is short-term. There are occasional infections for example dengue, where a second infection leads to a more severe outcome than the first episode.

In addition to policies aiming to reduce the number of new infections caused by one case (Ro), it is also important not to introduce new infections into the population. In the short-term, the reduction in international travel and social distancing will help reduce that. However, once there is control then there will need to be a significant response to prevent new infection chains being introduced from outside. That may include forced quarantine for 14 days when arriving on the island. Being an outlier in public health policy will isolate countries, and they will find borders that were normally open closed. The most pressing border for us is on the island. If such a major difference in policy continues, then ROI will have no option but to shut the border. If this were allowed to happen based on UK public health policies, the difference in policies would become clear. The South of Ireland is trying to emulate countries like South Korea, where the epidemic is under control and deaths will be considerably less. The UK policy is not quite clear. There was an initial good attempt to contain, and then mitigate. However, there was a change to suppression when the number of potential deaths seemed too large. There has been no attempt to systematically start reducing Ro to less than 1, the magic number needed to bring an epidemic under control. This suggests that there is still some reliance on the unproven herd immunity theory.

Initially NI public health policies were dictated by Imperial college London modelling data from a different island. NI wasn’t even in the original model. We continue to rely on centralized policies and seem unable to use the fundamental advantage we have of being an island with low population density. Just think why UK and Ireland are rabies-free compared to many other countries in the world. Cutting and pasting somebody else’s policies will not bring the best outcome.

Photo by 15734951 is licensed under CC BY-NC-SA

Claire Donnelly

I am an infectious diseases specialist with expertise in infectious diseases epidemiology.

I am not involved in the local response to Covid 19 and all thoughts are my own.