Epidemiology
By March 11, 2020, 105 countries had reported 118,319 confirmed COVID‐19 cases and 4292 deaths. 2  Outside China, large epidemics emerged in South Korea, Iran, and Italy. By March 14, 2020, approximately one in four COVID‐19 cases and deaths were in Europe. The US epidemic accelerated, with cases doubling every 6 to 7 days. 7  By March 29, 2020, more than 100,000 persons had COVID‐19 in the United States, the largest burden of COVID‐19 globally. 2 ,  7  As of April 29, 2020, the COVID‐19 pandemic has grown to more than 3 million confirmed cases and more than 206,000 deaths in 179 countries. The United States now has more than 1 million cases (33%) and more than 50,000 deaths (25%). 2 ,  7  The potential is high for large COVID‐19 epidemics in Brazil, Russia, India, and many African countries.
SARS‐CoV‐2 is transmitted directly through inhalation or mucosal surface exposure to an infected person’s respiratory droplets or indirectly when touching the face after contact with contaminated objects. 2 ,  4 ,  7  SARS‐CoV‐2 can remain viable on environmental surfaces for up to 72 hours. 8  SARS‐CoV‐2 is highly infectious with an R0 of approximately 2.2 to 3.0, meaning each infected person will infect about two to three other persons. 7  Large COVID‐19 outbreaks have occurred in health care facilities, households, cruise ships, religious services (e.g., funerals), and other large gatherings 1 ,  2 ,  7  Individuals can transmit SARS‐CoV‐2 before, during, and after symptomatic disease. As many as half of individuals with SARS‐CoV‐2 infection have no symptoms. 7