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expert comments about patterns of COVID transmission in the southern hemisphere and transmission in the winter

There has been discussion around patterns of COVID transmission in the southern hemisphere and transmission in the winter.


Prof Jose Vazquez-Boland, Chair of Infectious Diseases, University of Edinburgh, said:

“We have had accurate previews of what was coming during the first wave of the pandemic with the news from Wuhan in China and successively Italy, Spain and other countries.

“The peaks now detected in the southern hemisphere are a stark warning of what is coming next which I hope will not be ignored as has happened before.

“We have to be clear that the only way we have to control new COVID-19 outbreaks and epidemic waves, and to attempt eradicating the coronavirus in the absence of a vaccine, is the mass, systematic, regular screening of the population for subclinical carriers, which is where the bulk of the transmission comes from.”


Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said:

“South Africa and all of South America got their introductions of COVID-19 later than elsewhere in the world so we are still seeing their first waves.  These control measures have generally been ineffectively implemented across most of the Americas.

“Australia (Melbourne) may be more of a local flare up.  Only time will tell.  Australia also never had a big first wave with about 8000 confirmed cases in 25 million people. 

“The virus does not like heat and some aspects of humidity. How much this actually helps we do not know. The USA and India are going into their summer and seeing cases rise.

“It is far too early to draw any conclusions about how going into winter will affect this virus.  Winter in parts of Australia are very different from our winters.

“For the UK the main risk in winter may well be that we spend more time inside where social distancing is harder.  We know that outside transmission risks are very low especially if social distancing is maintained. 

“This is a new pandemic virus and comparisons with other pandemics through history are difficult and could be seriously misleading.  

“We need to learn as we go along and monitor any increase in cases very carefully.”


Dr Shaun Fitzgerald, Royal Academy of Engineering Visiting Professor, University of Cambridge, said:

“There are a number of factors which need to be considered for countries which are moving towards winter conditions, and these are relevant for us as we make preparations too.

Firstly, people may spend more time indoors than outdoors. The interior environment is inherently more challenging for us with this disease than outdoors – there are more potential contact points and it is not as easy to dilute any virus particles or have them swept away by the wind for example. However, winter conditions are more challenging in a number of other ways too. Although the interior environment can be drier (lower relative humidity) in winter, and there is some research which suggests that the virus prefers drier conditions, there is greater difficultly in providing plentiful amounts of fresh air. At the moment, we can throw open our windows and even doors, and get bountiful amounts of fresh air into many spaces. As the external temperature falls, this becomes more difficult as we don’t like excessively cold draughts. So, are we seeing instances where there is simply less fresh air being provided to interior spaces in the southern hemisphere?

“This challenge is something the Chartered Institution of Building Services Engineers is wrestling with at the moment. Lots of fresh air helps reduce the risk of transmission, and particularly so in environments that might otherwise be poorly ventilated. So, the key question is just how much air is really needed to reduce risks of transmission to a satisfactory level? The answer to this question will depend on many things such as the number of people in a given space, the prevalence of the disease, the rate of generation of virus particles by an infected person, the dwell time for people in a space, and ultimately the dose threshold for infection (which we still don’t know). Answering the question of ‘how much air is really needed’ will help us establish appropriate strategies for winter time ventilation.”


Dr Michael Head, Senior Research Fellow in Global Health, University of Southampton, said:

“Many countries are experience big increases in their daily COVID-19 cases. Whether or not these are second waves, or the first wave only now really starting to accelerate, it’s clear that COVID-19 is here to stay for some considerable time yet. Whilst we in the UK hope that cases will continue to decline here, the global threat is significant. There is also the potential for increases in UK cases as travel restrictions and local lockdowns are relaxed over the coming weeks and months.”


All our previous output on this subject can be seen at this weblink:


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