The graph shows the number of cases of Covid-19 as a fraction of national population, for some countries of interest. The data are from the
World Health Organization, except for the US data which is from the
NYT. The data may not all be reliable (eg both the BBC and the Washington Post have reported that Iranian hospitals have far more cases than is officially reported, and US testing and reporting still appears to be
shambolic).
The infection began and grew rapidly in China. You can see that the other countries have a pattern of a small number of cases that are well contained (folks coming from somewhere else who are in professionally managed medical isolation), followed by a "breakout" when the disease manages to slip the containment and start spreading through the general population. This leads (presumably after a delay) to a rise in cases. You can see that breakout in Korea around Feb 19th, in Italy about Feb 23rd, and late last week for the United States.
The data suggest that China has its outbreak well under control. However, this took extreme measures with huge economic impact: for example, there has been a
90% collapse in the rate of property sales. Korea also seems to be gaining control, and the growth rate of the Italian outbreak is declining. Both these countries and Iran have more cases, proportionally, than China.
The US curve is accelerating as testing becomes more widespread. The current growth rate of known cases is about 10x per week. The dashed line is an eyeball extrapolation, which suggests the US is one to two weeks from the level at which other countries have started taking measures like closing all their schools, quarantining cities, etc.
