The coronavirus is much, much more dangerous for the elderly than the young. A epidemiological study released several weeks ago by the Chinese Center for Disease Control and Prevention that found an overall COVID-19 case-fatality rate of 2.3 percent put the rate at 3.6 percent for those 60 to 69, 8 percent for those 70 to 79, and 14.8 percent for those 80 and older.

That obviously has implications for individuals as they assess the risks they face from COVID-19. It also matters for governments – because some places have a lot more old people than others.

Japan has the highest share of 65-plussers on the planet: 27.6 percent of its population in 2018, according to the World Bank. All the other countries where the percentage is above 20 percent are in Europe, with Italy leading the way at 22.8 percent. Italy is also the country with the second highest number of COVID-19 cases and deaths after China. That’s probably not a coincidence.

It’s not as if having a younger population will spare a country from major coronavirus trouble: Iran’s 65-plus share is just 6.2 percent, yet it seems overwhelmed by the disease. Still, it’s an indication that European countries with well-regarded universal health care systems will nonetheless face huge challenges as the disease spreads, and that nations in Africa and South Asia that are usually seen as especially vulnerable because of poverty and inadequate medical care may stand a chance of weathering this pandemic better than some rich countries do.

Among wealthy countries, the U.S. population share of those 65 and older is on the low end: 15.8 percent in 2018. Still, there are states with age profiles that look more like Europe’s, with Maine and Florida leading the way at 20.6 percent and 20.5 percent. In large part because of a big exodus of younger residents both before and after Hurricane Maria, Puerto Rico is even higher, at 20.7 percent. Utah has the lowest share, at 11.1 percent.

It’s when you break it down by county that the really big differences appear.

The county with the nation’s highest senior-citizen share is Sumter County, Florida, home of the fast-growing retirement community, The Villages. Its proportion of residents 65 and older was 55.6 percent from 2014 to 2018, a period I used when comparing counties because single-year data for many smaller counties aren’t reliable, and 57.6 percent in 2018. That’s an estimated 74,162 people 65 and older in a county with 277 acute-care hospital beds.

Apart from other retirement destinations in the South and Southwest, most of the old-skewing counties are in rural areas, which tend to have inadequate access to health care. On the positive side, the virus will probably take longer to get to such areas. Still the maps do indicate an imbalance of health care resources and likely severity of coronavirus consequences. Some of these place are going to really need help.