It appears that about 80% of those who died in China and Italy from COVID-19 were over 60-70. But for those who were younger, especially those in NY, it appears that obesity was one of the most common characteristics. This is likely related to insulin resistance that can be radically improved with diet strategies like time-restricted eating.
This new study in the journal Nutrients details precisely how exercise improves your immune system. There are many types of exercise but my absolute favorite is blood flow restriction training that I detail extensively in this article from earlier this year. One of the reasons it is so useful is that BFR increases nitric oxide, which is now being studied to treat COVID-19 at Harvard Medical School as reported in today's NY Times.
I have been exercising for over half a century and have never seen a strategy that improved overall metabolic and physical health as this strategy, especially in those over 60. You can use inexpensive $15 bands or treat yourself to the KAATSU system described in the article, which you might be able to justify if your gym is on lockdown.
Source:Physical Activity and Diet Shape the Immune System During Aging Nutrients March 4, 2020