Coronastream: Bubble burster

Posted on July 26, 2021   by Dr Tim Inglis

In this special blog series, medical microbiologists led by Dr Tim Inglis summarise some of the research that will be essential to inform COVID-19 countermeasures. Find out more about the project in Dr Inglis' Editorial 'Logic in the time of coronavirus', published in the Journal of Medical Microbiology

When acclaimed physician-journalist Dr Norman Swan says that “you can hear the worry in their voices” as he described the New South Wales Premier’s press conference on 12 July 2021, you realise things are not going well in Australia. At the time of writing, what started out as a small cluster of SARS-CoV-2 Delta variant cases in Bondi has grown into a significant outbreak whose chains of transmission snake out into regional centres. The state that was once described as the gold standard for COVID-19 control has gone the way of other states that didn’t manage to get things under control quickly. While hardly unique, this is an oddly Australian problem, where pride in disease suppression verges on hubris, and belief in COVID-19 elimination has become part and parcel of the rivalry with our trans-Tasman neighbour.
We have become such enthusiastic protectors of our shores against rampant viruses and anything else we can demonise, that a sizable chunk of the population just doesn’t get the importance of vaccination. Admittedly, there have been a series of missteps along what one commentator called our vaccine stroll-out. Obstacles to the acquisition, supply and access are no excuse for frustrating levels of vaccine hesitancy. The temporary suspension of the trans-Tasman travel bubble and the reinstallation of border restrictions between Australian states and territories have put yet another temporary stop to all but the most essential air travel. Maybe the prospect of lighter air travel restrictions for vaccinated adults is the incentive people are waiting for.
The science of COVID and SARS-CoV-2 continues to expand at breakneck speed, with a flurry of new insights to encourage those who struggle under the heavy load of pandemic responsibilities.

Congruence: the mental health burden of COVID-19

Quantifying the mental health burden of the most severe covid-19 restrictions: A natural experiment  

Fisher and colleagues sought to measure the effect on mental health of high degree public health restrictions during Melbourne’s second wave epidemic last year using a before and after survey method. In their first survey, there were no significant differences between Victoria and other parts of Australia, but in the second survey, they found almost double the rates of clinically significant depressive and anxiety symptoms in Victoria. While mental health consequences of severe public health restrictions are not surprising, the authors note that these effects are likely to impact psychological attributes needed for social and economic participation. This data can inform planning for psychological recovery and the protection of the most vulnerable.  

Consistency: environmental and socioeconomic factors affecting COVID spread 

Spread of COVID-19 in Zambia: An assessment of environmental and socioeconomic factors using a classification tree approach  

Phiri and colleagues used a machine learning technique known as tree classification to analyse geospatial data on COVID risk at district level in Zambia. A binary (COVID-19 versus no COVID-19) analysis showed that the most influential factors were distance to the airport, population density, distance to mines, to the town centre or the border, and lower rainfall. A graded risk level analysis suggested a co-location of high COVID-19 risk and high HIV infection rates. Low COVID-19 risk corresponded to locations far from urban centres and in hotter places. This study has wider application since its methods are widely accessible, and themes such as transport nodes and major industrial sites have immediate implications for other countries irrespective of their level of socioeconomic development. 

Cumulative dissonance: meteorological drivers of COVID-19 

Meteorological factors against COVID-19 and the role of human mobility 

This paper reports on the effects of weather on COVID-19 cases and deaths in 37 countries during 2020. Damette and colleagues considered direct physical factors affecting SARS-CoV-2 survival and durability, indirect social factors and how these impacted social distancing, cases and deaths. In addition to temperature and humidity, they found that solar radiation reduced cases and deaths. There were positive correlations between temperature or solar radiation and human mobility.  This led them to propose that the net weather effect is a result of the combination of a physical/direct negative effect and an indirect positive effect. Reducing direct weather effects on cases and deaths appears to be partly compensated by their indirect effects on mobility. This report goes some way to explain the apparently contradictory nature of previous studies on weather impact on COVID-19 and identifies previously neglected weather factors. Evidently, there is still a long way to go before the mechanistic links between climate, molecular biology and human infection are clear.  

Countermeasures: The investigation is the intervention 

Control strategies against COVID-19 in China: Significance of effective testing in the long run  

The deceptively short abstract to this paper succinctly captures Lin and Peng's observation that improved COVID-19 testing efficiency is more effective than city lockdown as an explanation for reduced case numbers. While the paper does not prove a causal link between improved testing efficiency and epidemic control, the advanced modelling techniques its authors use to make a strong case for using increased testing as a means of reducing reliance on travel restrictions and city lockdowns. Real-time population mobility data was used to ground the augmented simulation modelling. There is much in this account for the mathematically inclined, but also plenty of compelling figures that capture the impact of serial disease control interventions. Now we need a sequel dealing with the first six months of 2021, featuring the arrival of the Delta variant.  


New South Wales' Bondi cluster 
Australia's slow vaccine rollout