https://www.sciencedaily.com/releases/2020/04/200408184717.htm

The study estimates that in regions outside Hubei, the instantaneous reproductive number of COVID-19 -- the average number of cases generated by a single infected individual during the outbreak -- fell substantially after lock down measures were introduced on January 23, 2020, and has remained below 1 since then -- suggesting that the epidemic has shifted from one that is expanding rapidly to one that is slowly shrinking. (The higher the reproductive number, the more transmissible the virus is and the higher the risk for rapid spread. When the reproductive number falls below one, the epidemic is likely to die out.)

However, mathematical modelling to simulate the impact of relaxing current control measures, suggests that premature lifting of these interventions will likely lead to transmissibility exceeding 1 again, resulting in a second wave of infection.