英語で This graph has Tokyo’s authorities worried:
A total of 259 people infected seems like little cause for concern, especially in a metropolis of millions. However, as it has in other countries, that number does not entirely reflect the seriousness of the situation.
First of all, the number of infections in an area could double every three days (or even faster).
Second, this disease has an incubation period of around five days. Together with recommendations from health authorities in Japan to contact them after two to four days of symptoms, this means that most of the 259 people with Covid-19 were infected over a week ago.
Combine doubling with incubation and we have our first bit of bad news; the number of infections at this moment could well be over one thousand.
For the second bit of bad news, let us take the back of an envelope to check where doubling will take the numbers in one month:
Tokyo risks between 4000 and 83000 deaths if no measures are taken well within one month.
Every three days delay on top of that would double those estimates.