Covid-19 cases pass 100m

FOR ALL its deadliness the covid-19 pandemic—which has claimed the lives of more than 2m people—exhibits some fascinating mathematical properties. Take, for example, the virus’s “doubling rate”—how many days it takes for the number of cases to rise twofold. It took 12 days for the world to go from 1m to 2m cases in April and another 24 days to reach 4m cases in May. By early July, after much of the world had ramped up its testing capacity, global cases had doubled from 12.5m to 25m in 50 days. Some 70 days later, the tally had doubled again to 50m. On January 26th, precisely 80 days after that, the world reached 100m cases of covid-19. On current trends, cases will double again in 105 days.

These official figures understate the true extent of the pandemic. First, many cases were missed during the first wave when testing capacity was limited and so it appeared more deadly than it is (as demonstrated by the spike in the case-fatality rate observed in the spring, seen in the right-hand chart in the panel above). Second, coronavirus statistics are notoriously sketchy outside the rich world. Tanzania, for example, has not recorded a new case of the virus since May 8th—simply because testing in the country stopped. In December Turkey’s total caseload increased from 900,000 to 1.7m overnight after the authorities broadened the definition of covid-19 to include not just hospitalised patients but all those who had tested positive for the disease. In September, when cases numbered 32m worldwide, The Economist estimated—using the prevalence of covid-19 antibodies in surveys—that the true total was perhaps 20 times that figure.

Whatever the true number of infections, the data indicate that the number of new cases has recently hit new highs: over the past seven days 4.1m were recorded. Although the roll-out of vaccines offers hope that the latest wave of infections will eventually subside, there is still some way to go. According to data collected by Our World In Data, an online publication based at the University of Oxford, an impressive 23.4m vaccinations were administered in the seven days ending on January 25th, taking the total number of people who have received at least one dose to 62m. But most of the recipients live in North America, western Europe and rich countries in the Middle East. Just 3.1m doses have been dispensed in Latin America, South Asia and sub-Saharan Africa, countries that together are home to 3.2bn people. As our leader in the current issue explains, if the pandemic is a race between infections and injections, then infections are still ahead.