COVID-19 Update
We continue to update our summaries with developments regarding the two distinct processes of the disease and the epidemic.
We are rapidly developing an understanding of this disease. There is an evolving consensus of three potential stages. The first stage, the incubation period, patients typically have no symptoms, they may or may not have detectable virus. Many people recover without progressing. The second phase involves symptoms, typically not severe, the virus will be detectable. Most people will never get past this stage and will recover. In the third stage, there is the development of increasingly severe inflammatory or infective symptoms, especially involving the lungs. This leads to increasing cough and shortness of breath. This stage is associated with increasing viral load. In some patients this stage is associated with an excessive immune reaction which may lead to a ‘cytokine storm’. This is an overwhelming internal battle which can lead to damage not only to the lungs but other organs.
There are numerous trials of treatment ongoing internationally. The main focus of drug therapy is to impact either the ‘viral load’ or the immune response in order to prevent the progress of the disease into the third stage. Plasma from patients who have recovered has also been used with some success in China and studies are ongoing. Numerous vaccine studies are underway internationally. It remains possible that small quantities of experimental vaccine may be available for high risk health workers by late 2020. Realistically widespread vaccine supply is unlikely before Autumn 2021. This would be an incredible achievement.
Some factors clearly increase the risk of patients developing the more severe complications of COVID-19. Age, male sex, obesity, diabetes and high blood pressure are the most important factors. In Hong Kong patients are treated relatively early with a combination of antiretroviral medications and immune modulators. It is possible that the population in Hong Kong is generally fitter than other populations. Hong Kong also has widespread testing, which increases the diagnosis of milder cases. The current crude fatality rate in Hong Kong is 0.39% (4/1,018) which is a credit to the world class management within the public hospital system.
The epidemic curves in Europe continue to show signs of improvement and some of the initial pessimistic forecasts of mortality in both Europe and the US have been scaled back. We have explained previously the dangers of prediction of mortality early in epidemics. This is not a time for complacency. Just as we are gaining an understanding in hospital about the best management and treatment options for the disease, we are also increasing our understanding of the factors which work in controlling the epidemic. There is no question that social distancing and public health measures have been effective. As we described in previous articles, the challenge now is balancing the threat of the disease against the economic, social and political impact of the public health controls. Ultimately, unless an epidemic dies the only way in which a population can gain immunity against an infectious disease is naturally by infection, recovery and the development of herd immunity or by immunisation. It seems likely that a vaccine is 18 months away and the challenge is therefore to manage the spread of the epidemic, allowing the fires to burn in a controlled way whilst minimising the damage and stress on health systems and maintaining economic activity.
All infectious diseases have characteristics that can be measured in terms of a basic reproduction number R0. This number is a measure of, on average, how many people are infected by an individual with a specific disease. If this number is <1 the epidemic will die (this means that on average each infected person infects slightly less than one other person). If this number is >1 the epidemic is likely to grow. Infections with higher R0 values are more likely to spread. The department of Public Health at Hong Kong University has developed weighted models integrating big data and health data to create a real time effective measure of R0 in Hong Kong. We would like to thank everybody who responded for their support of the study we are undertaking with the public health department. The response was overwhelming, such that we filled the capacity within a few hours. We started blood testing this week. We must allocate testing to different age bands and those with, and without, a travel history. We are grateful for your understanding as we manage this process. We will communicate directly with everybody who registered interest. Data from this study will provide important information about background infection rates of COVID-19. The change in levels of population immunity will be a factor in evidence based public health policy decisions as we try to manage the transition from the current epidemic suppression to restoring normal social and economic life in Hong Kong.
As so often, time and more data is key. We now know that social distancing and public health measures are effective in controlling epidemic spread. The key missing data remains the population antibody studies. These studies will begin to be reported over the next few weeks. They will give us more evidence about the severity of the disease on a case by case basis, in addition to a greater understanding of population immunity levels. These factors will begin to drive the narrative regarding the balance between public health controls and restoration of economic and social activity.
We have described throughout this process the importance of recognizing the stress associated with lack of control and uncertainty. We have produced resources on health and well-being and suggestions for keeping fit whilst staying at home. COVID-19 is an unprecedented public health challenge. It is also unquestionably a significant disruptor. Notwithstanding the political narrative, which is inevitable in all epidemics of infectious disease, there has been unprecedented international medical collaboration. There are international trials on treatment, shared protocols and vaccine development. From telemedicine to zoom yoga sessions and living room marathons, the world will never quite be the same. It is important to focus on the positive.
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