COVID-19: top four science stories of the week

As confirmed cases of COVID-19 near 1 million worldwide, here’s a round-up of some of the latest scientific developments.

Two independent research studies have shown the benefit of receiving infusions of blood from COVID-19 survivors.

The teams – both based in China – extracted blood plasma from patients who had recovered from COVID-19, which contained antibodies against the disease. The first study from the National Engineering Technology Research Center for Combined Vaccines in Wuhan (uploaded to medRxiv and yet to be peer-reviewed) gave plasma to 10 patients who were severely ill with COVID-19. Six days after receiving the infusion, the COVID-19 virus was undetectable in seven of the 10 patients.

A similar study from Shenzhen Third People’s Hospital treated five ill patients with plasma from survivors. After 10 days three of the patients no longer needed ventilation.

The preliminary findings of this century-old technique come as patients in New York City and Houston have started receiving antibody-loaded plasma. No one really knows whether it will work or not but experts hope this approach will serve as a stop-gap and potentially help them to avoid having to turn away patients from crowded intensive care units. Provided that the blood is properly screened, the advantage of coronavirus-survivor plasma is that it’s readily unavailable, unlike drugs or vaccines which could take months or years to develop.

The latest analysis of data from the COVID Symptom Tracker app suggests a loss of sense of taste and smell may be the best way to tell whether someone has COVID-19.

The app, which was developed by a King’s College London team in association with the Guy’s and St Thomas’ NHS Foundation Trust, NIHR Biomedical Research Centre and a healthcare start-up ZOE Global LTD, asks users to log their symptoms (or lack thereof) daily. By the end of March, 1.8 million users in the UK had signed up to log their symptoms daily.

Between 24-29 March, 26% of the 1.5 million app users reported one or more symptoms; 1,702 of this 26% reported having been tested for COVID-19, with 579 positive results and 1,123 negative results.

In addition, 59% of those patients who tested positive for COVID-19 reported a loss of taste and smell, compared with just 18% of those who tested negative for the disease.

Despite not yet being added to the World Health Organization’s COVID-19 symptom list, lead researcher Tim Spector said: “When combined with other symptoms, people with loss of smell and taste appear to be three times more likely to have contracted COVID-19 according to our data, and should, therefore, self-isolate for seven days to reduce the spread of the disease.”

A study from Harbin Veterinary Research Institute in China suggests that cats can be infected with COVID-19 and spread it to other cats via respiratory droplets but other animals including dogs, chickens, pigs and ducks, are unlikely to catch the virus.

The results follow recent reports of a cat in Belgium being infected with COVID-19 a week after its owner began showing symptoms.

During the study (which was uploaded to the preprint website bioRxiv this week and is yet to be peer-reviewed), five cats were deliberately infected with COVID-19. Three of the cats were placed in cages next to cats that had not been given the virus. One cat became infected with the virus and researchers believe that transmission occurred via respiratory droplets. The findings were replicated in a second group of cats.

Virologist Linda Saif from The Ohio University in Columbus, who was not involved in the study, says that cat-owners need not be alarmed just yet as there is no direct evidence that infected cats can infect people and the study does not reflect real-life interactions between people and their pets.

During the SARS pandemic in 2003, similar studies showed that cats could be infected and pass it on to other cats but “there was no indication that SARS-CoV became widespread in house cats or was transmitted to humans”, Saif told Nature. Nonetheless, the authors of the study say that their work provides important insight into the animal reservoirs of COVID-19. Pet owners are advised to continue to follow usual precautions such as regular hand washing.

As COVID-19 has spread across the globe, researchers have been trying to figure out exactly how it is transmitted between people. The World Health Organization says that the virus is transmitted through droplets that are sneezed or coughed out, much in the same way that the common cold is spread, with current public advice reflecting that.

However, some researchers argue that there is preliminary evidence that the virus spreads in particles that are much smaller than droplets known as aerosols, which are less than 5 micrometres in diameter (more than 12 times smaller than the average diameter of a single human hair). They are advising increased ventilation indoors and in confined spaces as a precaution as aerosols can linger in the air for long periods of time and travel further than droplets.

Lydia Bourouiba, a researcher at the Massachusetts Institute of Technology (MIT) writes that she believes COVID-19 virus particles could travel up to 27 feet, based on previous studies of human sneezes. This is consistent with an earlier study from China that found virus particles could be found in the ventilation systems in hospital rooms of patients with COVID-19 yet it remains unknown whether there was any clinical implication of the finding. Other studies failed to find evidence of COVID-19 in air samples taken in isolation rooms.

The jury is out on whether COVID-19 is airborne or not, but many researchers agree that gathering conclusive evidence for airborne transmission could take years. In the meantime, increasing ventilation and wearing masks (with priority going to healthcare workers, those with symptoms and vulnerable populations) could be beneficial.