{"id":56,"date":"2020-05-19T08:29:00","date_gmt":"2020-05-19T07:29:00","guid":{"rendered":"https:\/\/drbannonsblog.aprendo.co.uk\/drbannonsblog_wp\/2020\/05\/19\/is-covid19-seasonal-will-it-just-go-away\/"},"modified":"2021-03-25T08:42:44","modified_gmt":"2021-03-25T08:42:44","slug":"is-covid19-seasonal-will-it-just-go-away","status":"publish","type":"post","link":"https:\/\/drbannonsblog.aprendo.co.uk\/drbannonsblog_wp\/2020\/05\/19\/is-covid19-seasonal-will-it-just-go-away\/","title":{"rendered":"Is COVID19 seasonal? Will it just go away?"},"content":{"rendered":"
The most optimistic view of the pandemic’s epidemiology is that it will simply peter out in the summer and disappear after effective lockdown measures have done their job. <\/span><\/div>\n

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Alternatively, there are those who state that the lockdown has made no difference at all and that nature is following its course.<\/span><\/div>\n

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So I decided to look at whats been happening and find out, as best as I can, where the truth lies. First, some good news from the front line:<\/span><\/div>\n

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Good news from London<\/span><\/h3>\n

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A recent study of health care workers<\/a> in a London hospital shows that the decline there is steeper than elsewhere in the country. The the red line shows the number of COVID positive patients and the blue, the COVID positive staff (right axis) in that particular hospital.  The brown bars shows the total number of positive patients in greater London (Left axis).<\/span><\/div>\n

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So, rates of infection are falling in the community, the staff and in patients.<\/span><\/div>\n

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This is good news, optimists predict that at his rate there may soon be no new cases in London, though I suspect there will continue to be outbreaks. <\/span><\/div>\n

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Epidemioloigy in London<\/b><\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
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<\/span>Can this all be due to the success of the lockdown? I doubt it’s the whole story.<\/span>

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So what is the effect of seasonality?<\/span><\/h3>\n

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The seasonality of flu is self evident but that doesn’t mean a different virus will behave the same way. Might a recent novel coronavirus outbreak in Germany give us a clue?<\/span>

<\/span>This graph show what happens to just such a novel coronavirus, a<\/span> <\/span>less disagreeable cousin of COVD19 <\/span>which caused croup in Germany. It was called <\/a><\/span>HCoV-NL63<\/a>, and this outbreak took place <\/span>during the winter of 2000. It clearly declined over March and disappeared by April.<\/span>

<\/span>COVID19 is far more transmissible and arrived here later in the winter, but you could argue that it might be behaving in similar way; fading out as the spring springs, the sun comes out and as vitamin D levels increase.<\/span><\/p>\n


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What coronaviruses tend to do<\/span><\/h3>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
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If COVID19 is behaving in anyway like this, then we could expect a natural decline at this time of the year. If true, this is also good news, but watch out for next winter. <\/span>

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Comparing countries<\/span><\/h3>\n


<\/span>Rates of infection are falling across all countries in the northern hemisphere. In some ways this might be what you would expect for a highly transmissible seasonal vira<\/span>l infection even without lockdown. The graph below shows the number of daily cases per million in the 10 hardest hit countries so far. <\/span>

<\/span>I can’t help but be struck by the similarities of the overall shape between countries, despite their differing approaches. Rapid increases, peaks in April and then variable declines. Interesting! <\/span><\/p>\n

 The dreaded “league table” is shown on the right side. <\/span>

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<\/span>In terms of daily deaths per million some differences do emerge, and the differences in outcome of different approaches become more clear, again the ‘league table’ is on the right. <\/span><\/p>\n

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<\/span>It seems to be that there are two things going on, similarities due to the natural history of the disease and different rates of control due to policy decisions.<\/span>

<\/span>If there is an effect of seasonality, the next place to look is the other side of the globe, as they enter their winter season.<\/span>

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What about Southern hemisphere?<\/span><\/h3>\n

<\/span>The patterns here are worryingly different. The bizarre behaviour of Bolsonaro at the helm in Brazil is accelerating deaths there, but the rates do generally seem to be climbing as they approach their winter, so seasonality is important. The impacts will be different too, with many more young people, but far less capable pubic services.<\/span>

<\/span>Also evident is that early aggressive measures in South Africa, New Zealand and Australia seem to be keeping their outbreaks under control. Again, a mixed picture.<\/span>

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Global cases are sadly, still increasing.<\/span> <\/div>\n
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Seasonality, Social distancing and Lockdown<\/span><\/h3>\n


<\/span>So as ever, the middle way seems to hold true; there is a definite effect of seasonality on the transmission of COVID19, social distancing and lockdowns have had effects too. For politicians to claim they have in any way ‘beaten’ COVID19 is nonsense, as is the claim the lockdown has made no difference. It’s true to say that:<\/span>
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