Latest COVID-19 science updates: care home residents with no symptoms, dementia genetics, and testing positive after recovery

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

Study find 60 percent of care home residents with coronavirus had no symptoms

A preliminary study has found that 40 percent of residents from four London care homes were infected with coronavirus, and that 60 percent of those had no or “atypical” symptoms.

The public health investigation carried out by a collaboration of doctors, academic and Local Authority officials, published on Tuesday, found that 26 percent of the residents died between March and May – three times the rate in previous years. All four homes had had coronavirus outbreaks.

In total, 313 residents and a random selection of staff were tested in the four homes. Four per cent of the tested staff that had no symptoms tested positive for coronavirus.

Dr Michael Head, Senior Research Fellow in Global Health at the University of Southampton, who was not involved in the study, said: “Alongside the death toll in the residents, it is important to note that across the four care homes covered, there were hundreds of staff, some of whom were agency staff and many of whom will work across more than one site. There are huge implications for transmission between care homes (and also hospitals), and the increased levels of employee sickness shows the difficulties in operating with safe levels of staffing.”

Study finds dementia gene may be linked with increased coronavirus risk in older people

Scientists have found that older people with a genetic mutation associated with dementia were also more likely to die from coronavirus.

Previous research has identified that dementia is one of the most common underlying health conditions of patients dying from coronavirus in the UK. But this study, published on Tuesday in The Journals of Gerontology: Series A , is the first to outline a possible genetic explanation for this observation.

The researchers from Exeter University used a genetic database of nearly half a million people from the UK aged between 48 and 86. From this genetic bank, the team identified any patients with “European ancestry” who were tested for coronavirus in March and April.

They then looked at the patients’ variations in a gene called ApoE, some types of which are associated with a high risk of dementia, and found that patients with the least common variant called e4e4 were more likely to have severe coronavirus.Importantly, the researchers pointed out that not all of these patients actually had a dementia diagnosis – suggesting that it was the gene variant itself which brought the increased virus risk, rather than dementia.

The gene variant plays a role in programming some of the body’s immune system, including inflammation production, which the study authors suggested could be how it influences coronavirus risk. The exact mechanism is still unknown, however, as is any definitive causal link between the gene variant and coronavirus.

Experts not involved in the study said the genetic association with coronavirus appeared robust, but noted that the genetic variant identified was still relatively rare so is unlikely to impact a large number of people.

Study suggests people can test positive for coronavirus after recovery

A study has found that some people are testing positive for coronavirus after they’ve recovered and been discharged from hospital.

The findings echo medical observations from around the world but don’t necessarily mean the virus is still transmissible after recovery. Rather it says that virus genetic material can still be present after clinical recovery, which can give a positive result on a PCR test.

The study, published in the JAMA Open Network on Friday, found that 10 patients out of 60 still tested positive when swabbed for the virus after leaving hospital.

Experts commenting on the study said it highlights some of the difficulties around using testing to comprehensively understand virus dynamics across a population.

Last week’s update can be found here.