Research news in brief

Less sensitive COVID-19 tests may still achieve optimal results if enough people tested

A computational analysis of COVID-19 tests suggests that, in order to minimise the number of infections in a population, the amount of testing matters more than the sensitivity of the tests that are used, according to research published in PLOS Computational Biology. Different states in India use different mixes of two main tests for COVID-19: a very sensitive reverse-transcriptase polymerase chain reaction (RT-PCR) test and a less sensitive rapid antigen test. Traditional thinking holds that an all-RT-PCR approach will ultimately lead to fewer overall infections. While RT-PCR tests are more sensitive than rapid antigen tests, they are more expensive and do not provide results immediately. Therefore, the precise mix of tests needed to optimise outcomes while accounting for cost constraints has been unclear. The researchers from the Ashoka University used computational models to conduct simulations of how COVID-19 spreads among a population, given different combinations of tests and the economic trade-offs between them. Accounting for the movement of people between different locations, they calculated the total number of infections that would occur by the end of a pandemic under each scenario. The analysis suggests that using only rapid antigen tests could achieve similar outcomes, in terms of total infections, as using only RT-PCR tests — as long as the number of people tested is high enough. This suggests that governments in lower and middle-income countries might be able to achieve optimal outcomes by concentrating on ramping up testing using less sensitive tests which provide immediate results, rather than favouring RT-PCR.

Mandating masks single most effective control measure in Melbourne’s COVID-19 second wave

The mandating of masks during Melbourne’s COVID-19 second wave in July 2020 was the single most important control measure and “turned the epidemic around”, new research from the Burnet Institute shows. The study, published in PLOS ONE, found a significant 20–30% reduction in the effective reproduction rate of the virus that correlated with that policy. The introduction of mandatory mask use by the Victorian Government on 22 July 2020, while Stage 3 restrictions were in place, turned an exponential increase in community transmission into an exponential decrease, almost overnight, the authors wrote. “We had a unique situation in Melbourne where masks were made mandatory as a single policy change, and compliance went from low use to very high use of masks in the community very rapidly,” they said. “It turned the epidemic around from case numbers that were increasing every day to a situation where we could see the numbers were getting back under control.” The study used thousands of images from The Age newspaper photo library of Melbourne community settings which showed mask usage rose from 43% before 22 July to 97% after. This matched almost perfectly with survey data from the SCRUB study led by collaborators at Monash University where, 3 days before the policy change, 44% of participants reported “often” or “always” wearing masks compared with 100% “always” 4 days after masks were made mandatory. “The key finding from this study is that masks work. They are an effective way to reduce COVID-19 transmission in the community. While using masks doesn’t mean that other restrictions to stop transmission may not be necessary, their use is a simple first step in our response to an outbreak. While we are confident that masks are highly effective indoors, we don’t know how much more effective they are indoors compared to outdoors. Importantly, given the growing evidence of outdoor transmission of the Delta variant, it makes sense that masks are worn both indoors and outdoors during a COVID-19 outbreak.”

Link between cognitive decline, bone loss and fracture risk in women

Researchers led by the Garvan Institute of Medical Research have discovered a link between cognitive decline and a faster rate of bone loss, and found that cognitive decline over 5 years increased future fracture risk in women. The association between cognitive decline and bone loss was weaker in men. The study of individuals aged 65 years and older was carried out over 16 years and has revealed a potential new approach to help identify older people who may be at risk of fracture. The team used data from the Canadian Multicentre Osteoporosis Study (CaMos), which documented skeletal health in people living in the community since 1995. The researchers looked at cognitive and bone health measurements of 1741 women and 620 men aged 65 years and older, who had no symptoms of cognitive decline at the beginning of the study. “After adjusting for all other variables, we observed a significant link between a decline in cognitive health and bone loss in women. This association was weaker and not statistically significant in men,” said the authors. “Interestingly, we also saw that cognitive decline over the first 5 years was associated with a 1.7-fold increase in future fracture risk in women in the subsequent 10 years. This was independent of the level of bone loss. While this study, published in the Journal of Bone and Mineral Research, could not identify a causal link, it suggests that cognitive decline should be monitored along with bone health, as a decline in one may signal the need for increased vigilance in the other. The researchers added that the link could potentially be mediated by a third factor, such as estrogen deficiency, which affects women after menopause and has been independently associated with both bone loss and cognitive decline.

Urgent need for antismoking campaigns to continue after pregnancy

Curtin University research has found quit support for smoking mothers should continue even after their first babies are born, given that many of those women will become pregnant again and that quitting can substantially reduce the risk of future preterm births. The longitudinal study, published in Nicotine and Tobacco Research, examined the records and histories across 23 years of 63 540 Australian women with more than one child, who smoked during their first pregnancy. “Our research found that for more than 30% of smoking mothers-to-be, quitting for their next pregnancies was achievable, and importantly could reduce the risk of early birth in subsequent pregnancy by as much as 26%,” the authors said. “While the benefit of quitting in reducing the harm to unborn babies is well established, less well understood was the prevalence of maintaining the quit message at the next pregnancy and the associated risk of preterm birth. What is clear from the study, is that maintaining quit messages and support for women who smoked during pregnancy, even after birth can have a significantly positive outcome for both them and their subsequent babies.”

Fewer deaths from melioidosis direct result of 30-year study

The number of deaths/mortality rate in Darwin from an infectious disease found mostly in the tropics, melioidosis, has decreased from 31% to 6% in the past 30 years, according to research published in The Lancet Infectious Diseases Journal. Melioidosis is a potentially life-threatening disease caused by the soil-dwelling bacterium, Burkholderia pseudomallei. The Darwin Prospective Melioidosis Study (DPMS) highlights the concept that B. pseudomallei is an opportunistic pathogen, meaning it causes serious illness in people with underlying health problems, while healthy people should not die if diagnosed and treated early. Melioidosis is a common cause of serious pneumonia and blood poisoning in the Northern Territory. The bacteria live below the soil’s surface during the dry season, but after heavy rainfall they proliferate and are found in surface water and mud. The Darwin study also provides evidence that the bacteria can become airborne during monsoonal weather events and cause melioidosis through inhalation. Lead author Professor Bart Currie from Menzies School of Health Research and Royal Darwin Hospital said the 30-year DPMS shows the importance of recognising diabetes and hazardous alcohol use as major risk factors for the severity of melioidosis, but people on immune suppressing therapy, including patients with cancer, are also at risk. “With early diagnosis and best antibiotics and intensive care unit treatment, healthy people should not die from melioidosis,” Professor Currie said. “Analysis of our 30 years of cases and links to weather also provides consistent evidence that global warming is likely to increase the risk of melioidosis in the future and expand the boundaries southward. With colleagues in Australia and overseas, we also have found that there are unexpected instances of melioidosis outside the tropics and more work is needed to understand these occurrences.”