Younger adults are generally more resilient than older people, but an increase in chronic health conditions among millennials, in their 20s and 30s now, has made them less hardy than they might think. They have seen rising levels of obesity and illnesses such as Type 2 diabetes and high blood pressure, as well as an increase in heart disease and some cancers. These are strongly associated with poor outcomes from coronavirus infection.

In addition, some 17 percent of men and 12 percent of women ages 18 to 44 smoke cigarettes, and 4 percent to 7 percent use e-cigarettes, according to national figures. Both increase the risk of respiratory illness.

How members of this generation will adapt to life during the pandemic might also dovetail with other problems. Compared with members of Generation X, in their 40s and 50s now, millennials have higher rates of behavioral health problems like depression — which affects one in 20 adults who are in their mid-30s, according to one report — and a significant number have alcohol and substance abuse problems, which are easily aggravated by social and economic turmoil and dislocation, experts say.

Millennials make up the largest share of the labor force and are a vital part of the economy, but they also face unique financial struggles. Many millennials juggle several jobs in the gig economy, and they are more likely than any other age group to be uninsured. Many are also burdened by student debt and contend with increasingly unaffordable housing. As a generation, they have borne the brunt of drug overdose deaths. Many have postponed marriage and starting a family for financial reasons.

While they have heard that by engaging in social distancing they can play an important role in reducing the spread of the coronavirus to others more vulnerable than they are, they are not immune.