By Dr. Anthony Policastro

One of the nice things about science is that data means everything. That is true as we continue with the COVID-19 pandemic. For that reason, I wanted to share the data to this point to show how we are faring in all of this.

I have been tracking the numbers since February 28. They look like this:

U.S. cases

Doubling every 72 hours

Feb. 28  – 60 cases

Mar. 2   – 125 cases

Mar. 5   – 250 cases

Mar. 8   – 500 cases

Mar. 11 – 1,000 cases

Mar. 14 – 2,340 cases

Mar. 17 – 4748 cases

Doubling every 48 hours

Mar. 19 – 9,500

Mar. 21 – 19,777

Mar. 23 – 35,079

Doubling greater than 48 hours

Mar. 26 – 68,000 (72 hours)

Mar. 29 – 131,403 (80 hours)

April 3  – 265,506 (5 days)

April 7  – 368,174 (greater than 5)

Delaware cases

Doubling every 72 hours

Mar. 14 – 8

Mar. 17 – 16

Doubling every 48 hours

Mar. 19 – 30

Mar. 21 – 45

Mar. 23 – 64

Doubling greater than 48 hours

Mar. 26 – 143

Mar. 29 – 232

April 3   – 450

April 4   – 593 (6 days)

Initially the total number of cases in the United States doubled every 72 hours. That occurred between February 28 and March 17. At that point things accelerated so that total number of cases started doubling every 48 hours.

Quarantine measures were not begun until March 13. Given the long incubation period of the virus, we expected to not see any effect until March 23. Between March 17 and March 23 the number of cases doubled every 48 hours.

At that point the quarantine measures started taking effect. From March 23 to March 26, they went back to doubling at 72 hours. From March 26 to March 29, it took about 80 hours to double. They did not double again until April 3 (over 5 days).

As of April 6 when I write this article we are at 368,174. That suggests that it will be more than 5 days to double the April 3 numbers.

The numbers for Delaware also showed a similar increase, but not to the same degree. For example it took six days to double the March 29 number. This suggests that we were doing better than the country as a whole.

It is more likely the huge increase in cases in New York City skewed the overall numbers. Over the two-week period between March 17 and March 31, New York City numbers doubled every 33 hours.

They went from 36 cases on the March 17 to 923 on March 24 to 38,000 on March 31.

For normal infections like the flu about 15% of the population gets what are called asymptomatic infection. They have the illness but no symptoms. However, they are still contagious.

It appears that we have a similar percentage of asymptomatic COVID-19 patients. Most infections have an incubation period of 48-72 hours. It is longer than that for COVID-19.

However in both cases patients are contagious while they are incubating the infection. Thus there are two groups of patients who are contagious. 

Some have no symptoms even though they are infected. Others do not yet have symptoms, but soon will. That is why there is now a recommendation for everyone to cover their faces when they go out.

They might be contagious and not know it.

Statistics are not limited to physician review. The best site for following overall cases is It not only shows the total number of cases but gives other information as well.

For instance there is a column that reports deaths per million people. The worldwide number is at 9.9 deaths per million. The United States is at 36. China is at 2. South Korea is at 3. Spain at 295 and Italy at 273 are much worse.

For those people wondering when quarantine measures will be relaxed, they do not need to wait to hear from government officials. They can follow the numbers and almost do the prediction themselves. Data is everything.