Objective: We describe the protocol for the LeCellPHIA project, a cell phone surveillance system that collects weekly population-based data on influenza-like illness (ILI) in Lesotho by calling a representative sample of recent face-to-face survey respondents.

Methods: We established a phone-based surveillance system to collect ILI symptoms from approximately 1700 respondents who had participated in a recent face-to-face survey in Lesotho, the Population-based HIV Impact Assessment (PHIA) Survey. Of the 15,267 PHIA participants who were over 18, 11,975 (78.44%) consented to future research and provided a valid phone number. We followed the PHIA sample design and included 342 primary sampling units from 10 districts. We randomly selected 5 households from each primary sampling unit that had an eligible participant and sampled one person per household. We oversampled those who were less likely to have a cell phone, and the elderly, as they are likely to be affected by COVID-19. A three-day Zoom training was conducted in June 2020 to train PHIA interviewers.

Results: The surveillance system launched July 1, 2020, beginning with a two-week enrollment period followed by weekly calls that will continue until September 30, 2021. Of the 11,975 phone numbers that were in the sample frame, 2,523 were sampled and 1,778 were enrolled.

Conclusions: The surveillance system will track COVID-19 in a resource-limited setting. The novel approach of a weekly cell phone-based surveillance system can be used to track other health outcomes and this protocol provides information about how to implement such a system.