dcale
commented
4 years ago @gagarine this is good input. We have however to watch out not to end up in a scenario where everybody gets regularly notifications. Because then people will either stop using the app or just ignore the notification.
"If the virus has spread too widely by the time an index case has been identified, it might be impossible to track the chain further, which makes contract tracing less valuable. This can happen, because people who have come in contact with the index case have, in turn, already spread the virus before they can get tested themselves." source: https://rega.kuleuven.be/if/tracing-tools-for-pandemics
It may be useful to inform contact at a second or more level to stop the spread faster.
A and B get in contact. B and C get in contact.
A get infected -> A inform B -> B inform C.
The paper highlight different factors that influces this: (a) How long does it take for potentially infected people to get diagnosed, if at all? (COVID-19 estimate: a few days to more than a week). The longer it takes for them to get diagnosed, the higher the risk that the virus has spread. (b) How infectious is the index case? For COVID-19, superspreaders have reportedly transmitted the virus to over 100 of their contacts, while others have not transmitted the virus to any of their contacts. We don’t yet know which proportion of infected are superspreaders. (c) How long after exposure does one become infectious? (COVID-19 estimate: 1 to 7 days). How long does infectiousness last? (COVID-19 estimate: sometimes up to one month). For COVID-19, apps should have a look-back time of at least one month. (d) What proportion of infected or diagnosed people is actually infectious? The current genetic COVID-19 tests identify acute infection, and as far as we know, these are all infectious. The majority of the quick tests that are currently being rolled out for COVID-19 identify antibodies against the virus, and these already develop when one is still infectious. However, when cured, one remains antibody positive, even after the virus has disappeared from the body and thus, one is no longer infectious. (e) What is the intensity of the outbreak? In other words, what is R0 (i.e. the average number of secondary cases caused by one case)? (COVID-19 estimate: 2 to 3). The higher R0 is, the higher the probability that the virus has spread beyond control. R0 can vary across contexts, as it depends on social structures (e.g. household composition, population density, levels of poverty and inequality) and cultural practices (e.g. how people greet each other). A high R0 also indicates that a larger proportion of new infections could be prevented if contact tracing is done early.