London: As nations prepare for the easing of lockdown rules Professor Sunetra Gupta’s research becomes ever more topical and relevant. Professor Gupta heads the Group for Evolutionary Ecology of Infectious Diseases in the Department of Zoology at Oxford University. In a conversation with The Sunday Guardian, Prof Gupta says she does not believe that the UK death rate will increase if the lockdown is lifted. She says, “It is plausible but unproven that the disease has already swept through and affected a large percentage of the population.”
In March, Prof Gupta published an exercise using a simple SIR model framework, which describes and captures the dynamics of certain pathogens by separating the host population into those susceptible and those who are recovered with an assumed immunity. All the UK modellers involved in Covid-19 research are agreed this is the correct basic framework to use, although others have enhanced the framework with more detail. Prof Gupta’s model showed that the risk of dying upon infection was a critical parameter; everyone agreed C-19 was a transmissible infection, at the time the R0 was thought to be between 2 and 4. The duration of infection was known to be 3-4 days to a week, the only unknown was how many were infected. The only data then and now is the cumulative death data, which has to be taken as accurate.
Imperial College assumed the epidemic had only just started as only a few deaths had occurred, and they used a high death rate of 1-2-3%. It is thought they used the data from the yacht Diamond Princess and Chinese studies. This model showed the peak was yet to come. Prof Gupta’s team showed that it was equally plausible that the epidemic had already peaked sometime in mid-March and a number of people had recovered, and deaths were happening with a time-lag of 2-3 weeks from infection; this model showed only 1 in 10,000 deaths and suggested a healthy percentage of herd immunity. Prof Gupta felt the virus was only very virulent in the small vulnerable fraction of the population. What was needed to inform the uncertainty about the true death rate and number of infections was wide ranging serological surveys.
Since then a talented member of Prof Gupta’s team, Craig Thompson has developed an antibody test that can also tell if the antibodies can neutralise the virus. The tests are currently being run on a variety of serum samples in her lab but the team are in discussions with Australia, Africa and other groups in Oxford about transferring this technology. The “Thompson” test is also being used to screen sera in plasma transfer trials and to assess the protective potential of monoclonal antibodies.
Prof Gupta’s group has obtained valuable results from a collaboration with the Scottish National Blood Transfusion Service to determine how many people have had the Covid-19 virus. They will also be assessing samples from ante-natal clinics and from healthcare workers. Prof Gupta feels secure in saying that reports from other parts of the world that suggest a fatality rate upon infection of 1%, is way too high, particularly since a substantial number of deaths occur in the vulnerable fraction of the population.
Due to international air travel and the peripatetic movement of people, Prof Gupta holds that the Covid-19 dribbled into UK during mid-December 2019 and escalated in mid-January. Prof Gupta believes it is critical to establish how many people are already immune through large scale serological surveys in order to construct a rational strategy to lead UK out of the lockdown. Scientists are currently sharing the raw data and cross-validating them so that these results can be national and accurate.
Prof Gupta’s updated research will be published in the next few weeks.