A long first wave of COVID-19 in Brazil that killed over 150,000 people is subsiding, with public health experts attributing the drop at least in part to a large number of uncounted people who caught the virus and developed temporary immunity. Continued social distancing among those able to work from home, mask wearing, and the warming weather as Brazil heads into the summer months, are also contributing to the fall in new infections, the experts said. Changes in behavior - like people flooding to bars due to a sense the worst is over - can quickly lead to a surge in new infections.