An important component of controlling the spread of infectious disease is reducing transmission.
One strategy to reduce transmission between people is to limit people’s movements and therefore the number of opportunities to contract or transmit the pathogen. For example, governments around the world introduced restrictions on mobility, such as lockdowns, curfews and mobility restrictions, during the COVID-19 pandemic in order to reduce transmission and control the spread of the disease.
We can analyse CDRs to assess the impact of government restrictions and their likely efficacy in reducing transmission.
Flowminder has analysed CDR data from the Democratic Republic of the Congo, Ghana, Haiti, Namibia and Sierra Leone to assess how population mobility changed over the course of the pandemic and in response to government actions. Furthermore, long-term monitoring of mobility, relative to a pre-pandemic baseline, also supported the assessment of how quickly areas were recovering from the impact of the pandemic and the associated government restrictions based on whether mobility has returned to its pre-pandemic level.
In Ghana, for example, the introductions of government restrictions in March 2020 resulted in decreases in population mobility across the country. The decrease in mobility was particularly large in the Greater Accra and Ashanti regions where lockdowns were introduced for the major metropolitan areas of Accra and Kumasi. During the lockdown periods, the daily number of trips between districts in these regions fell by approximately 60%. Lockdown measures in Accra and Kumasi were lifted in April 2020 and national restrictions were lifted in January 2021. By February 2021, mobility had returned to pre-pandemic levels in more than half of the regions. However, Accra and Kumasi appear to have experienced a slower recovery as mobility levels below baseline levels.
CDR data was similarly used to assess the impacts of government restrictions in The Gambia by a partnership between the University of Tokyo, the World Bank, The Gambia Bureau of Statistics, the Public Utilities Regulatory Authority and Gambian MNOs. Their analysis indicated that a substantial number of people left urban areas in response to lockdowns, which can have important implications for public health if this facilitated the spread of the SARS-CoV-2 virus to new areas. Similarly, peaks in mobility immediately following the announcements of lockdowns were identified from CDR data in Namibia and Sierra Leone. This could suggest that, while the lockdowns may limit mobility and therefore transmission, the initial response to lockdowns being announced may briefly increase transmission, making the timing and management of the announcement especially important.