More than six months into the pandemic, the coronavirus has infected more than 11 million people worldwide, killing more than 525,000.

Although she did not note this, 0.6 percent of the world’s population is 47 million people, and 0.6 percent of the American population is 2 million people.

At present, countries have very different case fatality rates, or C.F.R.’s, which measure deaths among patients known to have had Covid-19.

In most cases, that number is highest in countries that have had the virus the longest.

The United States was very close to that mark.

Those percentages are far higher rates than the 2.5 percent death rate often ascribed to the 1918 flu pandemic.

In the chaos that ensues when a new virus hits a city hard, thousands of people may die and be buried without ever being tested, and certainly without them all being autopsied.

Ten sizable countries, most of them in Western Europe, have tested bigger percentages of their populations than has the United States, according to Worldometer, which gathers statistics.

But their case fatality rates vary wildly: Iceland’s is less than 1 percent, New Zealand’s and Israel’s are below 2 percent.

Both figures — the infection fatality rate and the case fatality rate — can differ quite a bit by country.

Conversely, the figures should be higher in countries that lack oxygen tanks, ventilators and dialysis machines, and where many people live far from hospitals.

The C.D.C.’s estimate for the United States is lower: an I.F.R of 0.4 percent, according to a set of planning scenarios released in late May.

By comparison, 0.4 percent of the United States population is 1.3 million people.

To arrive at the C.D.C.’s new estimate, researchers tested samples from 11,933 people for antibodies to the coronavirus in six regions in the United States.

But the death rates may also shift in wealthier northern countries as winter approaches.

In each of the eight influenza pandemics to hit the United States since 1763, a relatively mild first wave — no matter what time of year it arrived — was followed by a larger, much more lethal wave a few months later, noted Michael T.

More than a third of all the people killed by the Spanish flu, which lasted from March 1918 to late 1920, died in the short stretch between September and December 1918 — about six months after a first, relatively mild version of what may have been the same virus broke out in western Kansas.