Imagine you are driving and hear on the radio: „Attention, in Canton Zurich, there is a wrong-way driver on the highway – to respect the driver’s privacy, we cannot disclose the location“. This would be crazy, right?

In public health, location data can be extremely powerful to understand and fight diseases. But did you know that permission to analyse location data is amongst the most difficult to obtain? The reason put forward is usually that location data can help identify a patient, who then could face abuse by neighbours but also companies such as insurances or pharmaceutical marketing. While these concerns should be taken seriously, I believe it is unethical to ban or overly restrict the use of location data for analysing and fighting life-threatening diseases.

Ironically, modern epidemiology and public health started with understanding where people get sick. John Snow observed clusters of cholera in proximity to a water pump (later found to be contaminated, London epidemic of 1854). Disabling that pump helped not only flatten the curve, but it also provided an important clue that the disease is spread by water (and not through bad smell called „miasma“, as believed until then).

You may say: location data would have been good to have to prevent the spread, but now that the disease is everywhere, it is too late. I disagree. Most likely a few cases will remain when we restart our economy. We will have to continue all the rules of hygiene and social distancing for a long time. Location data will be an important element in keeping COVID-19 under control until there is a cure against the serious forms of the disease or a vaccine.

Mapping that matches intervention options

Mapping the disease is not enough, we have to do the mapping on a scale that matches the intervention options:

For a country without the disease, it can be sufficient to know in which other countries the disease is ravaging. Taiwan used this approach to screen passenger arriving from high risk countries and to send them into quarantine (now every place outside Taiwan is high-risk, reason why all new arrivals have to quarantine). Other countries can do the same once they managed to lower the number of cases.

Within a country, more refined data is needed. Here we have to think of the different actors and what they aim to do – and provide them access to sensitive data as far as justified. Location can also be seen in a logical unit sense, thus connect people that have joint locations in common.

  • For tracing contacts of confirmed cases, very little personal data is really needed. Clearly for most cases, sharing data such as gender, age, profession or disease severity would not seem warranted. There is much hope in tracking-apps that are currently in development. However, these apps require the willingness of users to participate, so that traditional tracing of contacts is likely to stay for those cases that did not install an app, or do not have a cell phone, such as younger children. But also here, not much data is needed to find the contacts.
  • As a measure to enhance adherence to social distancing and hygiene rules, the general public should know about cases in their nearer community. Authorities can and should be transparent down to the zip-code, as long as they are not revealing associated data such as name, age or gender.
  • For commuters without tracking app, it will be important to learn about the commuting route and time of a case. This will allow them to assess if they have an elevated risk, and thus be more motivated to do self-health-checks.
  • As long as there is no strict mandate to wear masks in shops, it will be important for shoppers and authorities to learn about cases of (grocery) shop staff, especially if they are cashiers because they can exhale droplets containing the virus onto the purchased items. Actually, for shops that have customer reward cards (such as SuperCard or Cumulus in Switzerland), it would be technically easy to inform all customers who checked out at a positive-tested cashier during the infectious time window (though it would be difficult to find the right words and to put the risk into perspective).
  • For schools, it seems important to let the public know. Authorities need to be transparent. For the general public it will suffice to know that there were confirmed cases related to a school. More detailed data should be shared with pupils and staff that go from recommendations („two kids from another class were tested positive. Please perform enhanced social distancing for the coming two weeks“) to clear orders („Two of your child’s class mates were tested positive, we order your family to go into self-quarantine“) depending on how likely somebody may get infected.
  • For neighbors of cases, we need some balancing of values. Is it justified to tell people that „somebody“ in their apartment complex is a case? I believe this depends on two main aspects: where the disease was contracted and how well a case can be contained at home.
    If somebody got sick while in that building, everybody should learn that „somebody“ got the disease so that they can increase hygiene and self-health-monitoring.
    – In contrast, if a person returns sick from a longer journey, neighbours may not need to know about the presence of „somebody“ as long as that person can remain in perfect isolation.
    – However, they need to know if a returned sick person has to leave the apartment to get food, or if the person shares the apartment with healthy cases that cannot do total internal separation (e.g. shared bathroom). (In my view, authorities should allow home-isolation ONLY if total separation and isolation is possible.)

Location data is a precious good. We are in a special time so we should give permission to use location data where it seems scientifically justified and legally possible as long as there is still some form of oversight. After the crisis we may realise that some of the measures have gone farther than necessary, while for others more could have been shared. Therefore, whatever we decide now should come with an expiration date.

After the crisis is over, it will be important to have a public debate about the usefulness of location-based concepts for containing diseases in general. For example, I would not see any reason to be against a systematic collection and sharing of location data as long as this was limited to telling how many cases of a disease type happened in which ZIP-code, while I would be clearly against sharing refined data with neighbours for harmless or non-contagious diseases.


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P.S. Also in occupational hygiene, we use location information. An often used approach is to measure the exposure to chemicals at different places in the company, including where a chemical can go in case protection measures don’t work as intended. Another approach is to check the distribution of symptoms collected via questionnaires, or diseases reported by occupational physician.

Once we know the location of the problem, we can start analysing the situation and develop targeted solutions to improve protective strategies and to contain the hazard. Knowing which building or room has elevated levels is not enough. We need the location of release points and associated processes and operator actions before we can define measures that truly work.

Challenges typically faced by occupational hygienists are not only privacy questions related to worker data but also trade secrets. This is typically overcome by signing non-disclosure agreements and by anonymizing company data in reports that are made public.

In summary, occupational hygienists are familiar with the concepts of using location data and highly trained in defining strategies for controlling risks at the work place. It will be important to include occupational hygienists in the definition of measures to control COVID-19 in a restarting economy.