Ian Connellan
The numbers
Global COVID-19 deaths are set to pass the one million mark in coming days. The grim champion of most deaths per 100,000 population is tiny San Marino, a microstate in northern Italy. From a total population of about 34,000, it has recorded 723 cases and 42 deaths – that’s 124.32/100,000. At 98.06/100,000, Peru is the only other nation above 90.
Global
As at 16:47 CEST on Thursday 24 September, cases confirmed worldwide by national authorities stood at 31,425,029 (246,165 of them reported in the preceding 24 hours). 967,164 deaths have been recorded (4520). (Source: WHO Coronavirus Disease Dashboard)
Johns Hopkins University’s Centre of Systems Science and Engineering (CSSE) reported (at 15:30 AEST on Thursday 24 September) 31,779,835 confirmed cases and 975,104 deaths.
Australia
The Department of Health reported on 23 September that national confirmed cases stood at 26,973, a rise of 22 in 24 hours. 859 deaths have been recorded. More than 7,393,500 tests have been conducted (0.4% positive).
State by state: ACT 113 total cases (first case reported 12 March); NSW 4212 (25 January); NT 33 (20 March); Qld 1153 (29 January); SA 467 (2 February); Tas 230 (2 March); Vic 20,100 (25 January); WA 665 (21 February).
Research
First or second wave?
Mathematicians Max Menzies, from Tsinghua University, Beijing, and Nick James, a PhD candidate at the University of Sydney, have developed a model to determine whether US states are in a first or second surge of COVID-19. They’ve published their work in the journal Chaos.
The pair studied data from all 50 US states and the District of Columbia from 21 January to 31 July. They found that 31 states and DC were experiencing a second wave as of the end of July.
Their method smooths raw daily case count data to eliminate artificially low counts over weekends and even some negative numbers that occur when localities correct errors. After smoothing the data, a numerical technique finds peaks (P) and troughs (T), from which turning points can be identified.
A turning point occurs when a falling curve surges upward or a rising curve turns downward. Only those sequences where the P and T amplitudes differ by a certain minimum amount are counted. A second wave that’s less than one-fifth the size of the first doesn’t qualify as a “second wave” – it’s just too small.
Thirteen states – including California and Texas, the US’s most populous – had increasing case numbers throughout the entire seven-month period studied and are considered to be still in their first wave. Another 31 states showed sequences of the form TPTP – zero cases to a first peak, then another trough and peak. This is the signature of a second wave.
New York and New Jersey completely flattened their curves by the end of July. The analysis confirms these two states experienced just one wave.
“In some of the worst performing states, it seems that policymakers have looked for plateauing or slightly declining infection rates,” says James. “Instead, health officials should look for identifiable local maxima and minima, showing when surges reach their peak and when they are demonstrably over.”
“The real moral of this paper is that COVID-19 is highly infectious and very difficult to control,” says Menzies.
The authors have also applied their method to analyse infection rates in eight Australian states and territories. The Australian analysis hasn’t been peer-reviewed but it applies the peer-reviewed methodology. The analysis clearly identifies Victoria as an outlier, as expected.
“What the Victorian data shows is that cases are still coming down and the turning point – the local minimum – has not occurred yet,” says Menzies, and from a mathematical perspective at least, Victoria should “stay the course”.
Fine weather for COVID
With winter approaching in northern hemisphere coronavirus hotspots, an understanding of the effect of weather on the virus’s spread is timely.
A paper published in Physics of Fluids reveals results of a study into the effects of relative humidity, environmental temperature and wind speed on the respiratory cloud and virus viability.
Researchers found that a critical factor for the transmission of infectious particles in respiratory clouds of saliva droplets is evaporation.
“Suppose we have a better understanding of the evaporation and its relation to climate effects,” says author Dimitris Drikakis, of the University of Nicosia, Cyprus. “In that case, we can more accurately predict the virus concentration and better determine its viability or the potential for virus survival.”
Despite the importance of airborne droplet transmission, research regarding heat and mass transfer around and within respiratory droplets containing the virus has been scarce.
“We found high temperature and low relative humidity lead to high evaporation rates of saliva-contaminated droplets, thus significantly reducing the virus viability,” says co-author Talib Dbouk.
Additionally, the researchers observed the travel distance and concentration of the droplet cloud continued to be significant, even at high temperatures if the relative humidity is high. Wind speed is another crucial factor that might alter all the rules for the social distancing guidelines.
The findings help explain why the pandemic increased during July in crowded cities around the world, such as Delhi, which experienced both high temperatures and high relative humidity.
It also provides a crucial alert for the possibility of a second wave of the pandemic in the coming autumn and winter seasons, where low temperatures and high wind speeds will increase airborne virus survival and transmission.
The study adds to the growing body of research that reinforces the importance of social distancing and the use of face masks to prevent full virus spread.
The asymptomatic minority
There’s been plenty of talk about individuals with SARS-CoV-2 infections and no symptoms, and a new study published in the open-access journal PLOS Medicine addresses the question of what proportion of total infections these cases represent.
Diana Buitrago-Garcia from the University of Bern, Switzerland, and colleagues suggest that true asymptomatic cases of COVID comprise a minority of infections.
The full spectrum and severity of COVID-19 symptoms are not well understood. Some people experience severe infections resulting in viral pneumonia, respiratory distress syndrome and death. Others remain completely asymptomatic or develop mild, nonspecific symptoms.
To better understand the proportion of people who become infected with SARS-CoV-2 and never develop any symptoms, as well as the proportion of people who are asymptomatic at the time of diagnosis but develop symptoms later, researchers systematically reviewed literature using a database of SARS-CoV-2 evidence between March and June.
While the study was limited by its inability to ascertain the impact of false negatives, the researchers were able to estimate that 20% of COVID-19 infections remained asymptomatic during follow-up.
“The findings of this systematic review of publications early in the pandemic suggests that most SARS-CoV-2 infections are not asymptomatic throughout the course of infection,” wrote the authors.
“The contribution of presymptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention measures, with enhanced hand and respiratory hygiene, testing and tracing, and isolation strategies and social distancing, will continue to be needed.”
Research bites
According to a new study from The George Institute for Global Health published in the Journal of Addiction Medicine, the COVID-19 pandemic has more than doubled the number of smokers wanting to quit but a different approach may be needed to help them succeed. Lead author Simone Pettigrew says it was good to see positive intentions, but the right support was needed to ensure successful follow-through. “Most smokers want to quit, and many have tried unsuccessfully in the past,” she says. “COVID represents an important opportunity to help them use proven support tools while their motivation to quit is high.”
Preliminary findings from the University of South Australia’s ongoing Annual Rhythms in Adults’ lifestyle and health (ARIA) study (which isn’t peer-reviewed) suggest that effect of lockdown on people’s lifestyle and wellbeing was not as bad as we might have expected. During the lockdown period of February to April, on average people slept longer, got up later, did less light physical activity, drank a bit more alcohol and ate a little less protein. The findings also noted no changes to weight, dietary energy intake, quality of life or symptoms of depression, anxiety or stress.
“Given the unprecedented nature of lockdown, we expected to see greater levels of anxiety and depression – and perhaps even increases in weight as people were at home and had greater access to their fridges – but no,” says researcher Rachel Curtis. “All in all, it’s reassuring to see just how resilient Australians were in terms of their health and wellbeing during lockdown.”
A new study on the health sciences preprint server medRxiv suggests that herd immunity played a role in the size of the COVID epidemic in the Brazilian city of Manaus. SARS-CoV-2 initially spread rapidly through the 1.8 million-population city, but since the peak in May new cases and deaths have rapidly fallen. The joint Brazil/UK research team says that’s because the virus is running out of hosts. “Although non-pharmaceutical interventions, plus a change in population behaviour, may have helped to limit SARS-CoV-2 transmission in Manaus, the unusually high infection rate suggests that herd immunity played a significant role in determining the size of the epidemic,” the authors write.
Researchers claim that COVID-shutdown-related reductions in human-made noise has seen birds in parts of California adapt their songs to be higher quality. The study, published in Science, provides strong evidence that previously reported regional changes in birdsong, which lowered song quality and affected male birds’ ability to defend their territories, resulted from increased anthropogenic noise. The study focused on birdsong in urban and rural populations of white-crowned sparrows in the San Francisco Bay area, the subject of many years’ observation by researcher Elizabeth Derryberry and colleagues. The authors say that results reveal how quickly birds can adapt to changing environments and suggest that lasting remediation might lead to other promising outcomes, including higher species diversity.
In a Correspondence in Nature, geneticist Paul Nurse, astronomer Martin Rees, former UK prime minister Gordon Brown and colleagues write that with the Brexit transition period ending in just three months, it’s now impossible to develop separate UK equivalents to European Union and European Commission science and knowledge-exchange programs. “Anything less than continued UK association with these programs will be catastrophic for both British and European research,” write the authors, who claim such programs have a total value approaching €100 billion (AU$165 billion) over their lifetimes. The authors conclude: “As we weather the worst public-health crisis in living memory, now is the time for the United Kingdom to be leading and enhancing scientific collaborations with our European partners, not leaving them.”