I can't be sure, but I imagine this would be offset by the productive segment of the older population who die from the virus. Older workers are valuable because often they have the widest experience and are best able to train others.
Ah, I misread it. Interesting concept but the point is sort of moot since a virus can't specifically target people who dont work. Sure, a virus can be more likely to be fatal in older people, but there are still a lot of older people who work, and enough unproductive young people that i still think it would be a net negative.