COVID-19: Top science stories of the week, from asymptomatic spreading to surface risk within households

People who feel fine might unknowingly be a source of infection

New research comparing asymptomatic and symptomatic cases in Vietnam suggests that infected individuals who never show symptoms can pass the virus to others.

Of roughly 14,000 people tested in Ho Chi Min City between mid-March and early April, 49 tested positive for the virus. Researchers at the Oxford University Clinical Research Unit in Ho Chi Minh City monitored 30 of the 49 individuals and found that 13 (43%) did not develop symptoms.

Contact tracing revealed that two of the asymptomatic patients were “highly likely” the origin of at least 2-4 further infections, adding to the growing evidence that asymptomatic, and pre-symptomatic individuals can unknowingly transmit the virus to others. The study has been accepted for publication in the Clinical Infectious Diseases journal.

This comes in a week where experts at the World Health Organization clarified that the percentage of all Covid-19 cases that are asymptomatic is still unknown, as is how the virus is transmitted if these individuals are not coughing.

Surfaces could pose only a modest risk for household spread

In what could be good news for households with self-isolating individuals, new research out this week suggests that the risk of coronavirus transmission via household surfaces is relatively low.

Researchers at the University of Bonn analysed the air and various household surfaces for coronavirus in 21 German households in which at least one person tested positive for COVID-19.

None of the air samples tested positive for the virus, and only 3.36 % of all object samples tested positive. Some (15.15%) wastewater samples from washbasins, showers and toilets tested positive for the virus, but it is not known whether wastewater is a source of infection for people who co-habit. More research is needed to understand whether aerosolization of viral loaded droplets from wastewater reservoirs is possible.

Importantly, there was also no statistically significant correlation between the amount of virus detected on household surfaces and in wastewater and the extent of infection spread inside the household.

The findings, not yet published in a journal, suggest that direct transmission of the coronavirus, for example through exhaled or coughed droplets, is probably the main route of infection within households.

What’s the risk for people with HIV?

That’s the question researchers in the United States are trying to answer by examining the medical records of people living with HIV who have also had Covid-19.

HIV can weaken the body’s ability to fight off infections, but little is known about the risk of COVID-19 complications for people with HIV/AIDS.

On Tuesday, South Africa’s Western Cape Department of Health released the first set of data that showed that people living with HIV had a 2.75 times increased risk of death from COVID-19. It also found that HIV positive people on treatment, who are virally suppressed, and those who are not virally suppressed, both had an increased risk. However, the data has not yet been scrutinised to check that the higher risk can’t be accounted for by other risk factors such as diabetes, obesity and living in poverty.

The newly launched study, which includes researchers at the Fred Hutchinson Cancer Research Center, University of California San Diego and the University of Washington, hopes to address this knowledge gap and answer several questions, including: Are people living with HIV at higher risk of complications if they contract Covid-19? What factors might predict which patients are most at risk? Are people with HIV who contract Covid-19 more likely to be symptomatic? And are people with HIV more likely to die if they do contract the new coronavirus?

In other news, after a turbulent few weeks for hydroxychloroquine trials, further studies rule out the malaria drug as having any benefit.