Public health work of the past reveals important strategies in disease prevention. An example is the pioneering disease-mapping approach of leading epidemiologist and public health figure, John Snow, through the analysis of areas affected by the 19th-century London Cholera pandemic to identify the source of infection (Begum, 2016). This prevention strategy speaks to the current COVID-19 pandemic where no vaccine is available yet, and the incidence and mortality of the disease can be tracked using global statistics such as those used by Johns Hopkins University (JHU, 2020). 

In the absence of drugs or vaccines, Snow used research that diverged from theories of diseases being solely spread through pollution or ‘bad air’ by mapping cholera cases across London.

Several countries are struggling with containing COVID-19 (Freeman, 2020), and the ongoing pandemic indicates that strong health care systems are required to prevent, detect, contain, and treat outbreaks (OCED, 2020). This article seeks to underline the importance of disease mapping for effectively planning and responding to challenges during the pandemic.

John Snow’s public health work

In the absence of drugs or vaccines, Snow used research that diverged from theories of diseases being solely spread through pollution or ‘bad air’ by mapping cholera cases across London. Prior to the development of germ theory, his use of statistics successfully identified the disease source as an infected water pump. This was achieved by speaking to local residents and mapping deaths from the outbreak, revealing that several mortalities were clustered around a water pump located nearby. The local council authority disabled the pump further to these findings being presented. Snow’s research is commonly cited as effectively leading to the end of the outbreak, alongside birthing a new approach towards disease prevention and surveillance that is still used today (Begum, 2016). The application of epidemiology statistics alongside collaboration with local government and community highlights the intersecting layers of public health and the value a multi-layered approach holds for investigating and preventing the spread of COVID-19.

Behaviours related to infection: value of effective public health strategy

Countries must promptly collect, analyse, and disseminate accurate, timely data about the epidemiology of COVID-19 to understand areas most affected, the demographics of those affected, the severity of symptoms, and trends across incidence and mortality.

Following WHO’s declaration of the pandemic, Germany rolled out early testing capacities, higher levels of testing, an effective containment strategy amongst the elderly, and efficient use of hospital resources and capacity.

These approaches can inform public health action (Public Health England, 2020) with mounting evidence showing that surveillance has helped in containing the crisis. For instance, following WHO’s declaration of the pandemic, Germany rolled out early testing capacities, higher levels of testing, an effective containment strategy amongst the elderly, and efficient use of hospital resources and capacity (Our World In Data, 2020). The analysis of movement restrictions for persons at high risk of infection is also integral (Africa CDC, 2020). Strict hand hygiene measures should be implemented in congregate settings and respectful social distancing should be supported in settings at high risk of widespread transmission such as school closures (Africa CDC, 2020). The targeted continuous use of medical masks by health workers in health facilities and non-medical masks by the general public using a risk-based approach is also important (WHO. 2020a).

Building on Snow’s research by adopting effective surveillance strategies, alongside promoting non-pharmaceutical interventions such as rigorous hand hygiene measures and the use of masks in public health campaigns is therefore vital to limit the spread of COVID-19. COVID-19 is primarily transmitted via respiratory droplets and contact routes. Droplet transmission occurs when a person is in close contact (within 1 meter) with an infected person and is exposed to potentially infective respiratory droplets (WHO. 2020a). Airborne transmission may be possible where aerosol-generating procedures are performed (WHO. 2020a).

The WHO has been working with the scientific community to evaluate whether COVID-19 spreads through aerosols in the absence of aerosol-generating procedures, particularly in indoor settings with poor ventilation (WHO, 2020b). The results can explain ‘super spreader events’ such as scenarios where entire groups have become infected (GAVI, 2020). Ongoing research on this has major implications for disease control and lockdown measures (GAVI, 2020), highlighting the importance of adapting evidence-based disease-mapping methods.

Adapting and widening Snow’s localised approach through the use of a website form and mobile app, this system allows anyone with symptoms to record their status and get tested.

Community transmission of COVID-19 is defined (2020) as “experiencing larger outbreaks of local transmission defined through an assessment of factors including, but not limited to: large numbers of cases not linkable to transmission chains; large numbers of cases from sentinel lab surveillance; multiple unrelated clusters in several areas of the country/territory/area” (WHO, 2020c). Data indicate that COVID-19 is efficiently transmitted in a community setting (Cowling et al, 2020). Contact tracing is an established public health measure that helps prevent community transmission by targeting clusters that may lead to new outbreaks. It has been an integral factor in the response of several countries to reduce cases (HSC Public Health Agency, 2020). A prime example is the NHS Test and Trace system (Public Health England NHS, 2020). Adapting and widening Snow’s localised approach through the use of a website form and mobile app, this system allows anyone with symptoms to record their status and get tested. It also traces recent contacts of anyone who tests positive and, if necessary, notifies them to self-isolate to prevent further spread. It aims to control the rate of reproduction (R) and reduce the spread (UK Government, 2020).

Faced with the challenge of rising incidence rates (Cowling et al, 2020), population health can be improved by using insights from Snow’s disease-mapping methods in the current age of ever-increasing technological opportunity with BigData.

As organisations work to develop a COVID-19 vaccine, the use of disease mapping based on surveillance and epidemiological statistics is an effective strategy for prevention. 

By Nkengfua Blaise

Contributor and member of the Cov360 team

9 September 2020

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