African countries’ easing of COVID-19 controls and the emergence of more transmissible coronavirus variants fueled a second wave of infections more severe than the first, according to a study published in The Lancet journal.

Rapid and coordinated government responses likely limited the impact of the virus on the continent in the early stages of the pandemic, wrote authors including Stephanie Salyer, an adviser to Africa Centres for Disease Control and Prevention.

Many countries implemented strict controls more than two weeks before reporting their first case, they said.

Yet daily infections were about 30% higher during Africa’s subsequent second wave, as lockdown measures were loosened amid economic necessity and adherence to basic health protocols declined, according to the study.

The authors analyzed cases and tests carried out across all 55 African Union member states between Feb. 14, 2020 and Dec. 31, when more than half of these countries had or were experiencing a resurgence of infections. While notable variants only emerged near the end of that period, they are likely to have at least partly driven the surge, they said.

More than three quarters of the continent’s more than 65,000 recorded Covid-19 deaths have occurred in South Africa, Egypt, Morocco, Tunisia, and Algeria. Cases throught Africa contributed about 3% of the global total in 2020.