22 Apr 2020

Latest COVID-19 science updates: antibody tests, air pollution and why the virus may be so infectious

As the COVID-19 pandemic unfolds, scientists are rushing to carry out and publish research which will help us understand how the virus works, and how the disease it causes can be treated.

Each week, Channel 4 News will provide a summary of key research papers, studies or developments from the world of COVID-19 science.

Preprint study on effectiveness of commercial antibody kits (published 20/04/2020)

A study by a group from Oxford University tested several commercially available rapid antibody kits and found that those tested were not  reliable enough to confidently prove whether an individual had been exposed to coronavirus or if they were immune.

However, the research did suggest a step forward has been taken in developing a lab-based immunology test for antibodies, which may be used in hospitals.

The study used these lab-based tests as an accuracy benchmark against which to judge the rapid home tests – the cheap ‘pregnancy type test’ that could potentially be used at home by the general population.

The study was a preprint, so hasn’t yet been fully peer reviewed, and only used a sample of 40 patients.

Eleanor Riley is Professor of Immunology and Infectious Disease at the University of Edinburgh, and was not an author on the paper. In comments to the Science Media Centre, she said:

“This is a really useful paper. It shows that the problem with the commercial rapid antibody tests is that they are not sensitive enough – they fail to pick up antibodies in over a third of people who do in fact have antibodies. However, these tests do have acceptable levels of specificity – that is, they are only picking up people who have genuinely been exposed to the COVID-19 virus. This means if your test is positive, you can be confident that you have been infected and have antibodies. But if your test is negative, you can’t rule out that you might have been infected.

“Just as importantly, this paper shows that we do have a very good assay for use in the lab. The ELISA assay showed excellent sensitivity and specificity. This means that public health labs now have a test that they can use to begin to understand what percentage of the general public have already been infected.”

This means the rapid tests do not meet the regulations set by UK regulators.

The research also suggested that all antibody tests are most reliable 10 days after infection by the virus.

The study didn’t find a link between the concentration of antibodies found and disease severity. Several experts have suggested previously that more antibodies would be produced in response to more severe disease, but that isn’t backed by this study.

Preprint study on impact of air pollution on coronavirus mortality in England (published 20/04/2020)

A preliminary study has been published which suggests that people in more polluted parts of England are more likely to die from coronavirus.

This follows several recent studies from across the world suggesting similar findings relating to air pollution and the virus.

Specifically, the study suggested that nitrogen oxides and ozone – both produced by cars and by industry – are associated with higher coronavirus morbidity.

Many experts commenting on the findings said that the premise of the study is correct – air pollution has been proven to cause respiratory problems, which intuitively would then predispose people to coronavirus.

But many experts said this study does not prove a causal link between air pollution and the virus in England.

They noted several limitations in the study which do not account for the high specificity of air pollution impact, such that one street may be exposed very differently from an adjacent street.

Dr Liam Brierley, a biostatistician from University of Liverpool who was not an author on the study, said:

“Other research available does demonstrate that air pollution may be important for COVID-19 as regions with higher air pollution are more likely to have greater prevalence of chronic respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD), which can affect COVID-19 disease severity. Air pollution is therefore still an important consideration in public health responses to pandemic respiratory infections, though much more detailed research will be necessary to fully understand how this affects COVID-19 risks for the UK.”

Nature Medicine study looking at timing of coronavirus transmissions (published 15/04/2020)

A study published in Nature Medicine has suggested that the coronavirus may be most infectious before symptoms of the disease begin.

The paper looked at two things. In 94 confirmed coronavirus cases it found that viral load – the amount of virus present in an infected individual – from patient throat swabs was highest at the point of symptom onset.

Secondly, it modelled the transmission between a separate sample of 77 infected pairs. Here it estimated that in 44 per cent of the pairs, transmission occurred before symptom onset.

The authors said that together the findings suggest the virus could be most infectious just before symptoms begin.

Using models the authors suggested that viral shedding – the release of the virus which can potentially transmit – may begin two to three days before the first symptoms begin.

This high presymptomatic transmission may explain why the virus has been so infectious around the world.

In comments to the Science Media Centre, William Keevil, Professor of Environmental Healthcare at University of Southampton who was not an author on the study, said:

“This new study in Nature Medicine adds to the growing evidence around the world of there being significant numbers of asymptomatic, presymptomatic and also low level infection patients showing minor symptoms that are difficult to recognise, trace and isolate without rapid diagnostic virus tests such as RT-PCR being available.”

Some experts commenting on the findings suggested that they added to the body of evidence suggesting masks should be worn by everyone, as transmissions can occur before someone knows they’re infected.

Last week’s update can be found here.