  The world is suffering from a pandemic called COVID-19, caused by the
SARS-CoV-2 virus. National governments have problems evaluating the reach of
the epidemic, due to having limited resources and tests at their disposal. This
problem is especially acute in low and middle-income countries (LMICs). Hence,
any simple, cheap and flexible means of evaluating the incidence and evolution
of the epidemic in a given country with a reasonable level of accuracy is
useful. In this paper, we propose a technique based on (anonymous) surveys in
which participants report on the health status of their contacts. This indirect
reporting technique, known in the literature as network scale-up method,
preserves the privacy of the participants and their contacts, and collects
information from a larger fraction of the population (as compared to individual
surveys). This technique has been deployed in the CoronaSurveys project, which
has been collecting reports for the COVID-19 pandemic for more than two months.
Results obtained by CoronaSurveys show the power and flexibility of the
approach, suggesting that it could be an inexpensive and powerful tool for
LMICs.
