This is as interesting as the time I learned from an expert talking about research into aging that technically younger animals (and likely people) can experience aging if they're injected with the blood of an older counterpart, suggesting (among other arguments he made) not just that it's "contagious" but that aging should be treatable and youthful physical health could be extendable to longer ages.
Alternatively, you can have rejuvenating effects on cells by injecting older patients with a young persons blood.
It's cool, but any time I start thinking about it, I end up flooded with horrible depictions of dystopian levels of abuse that's likely to result from this becoming a trend among the uber-rich.
Twenty years ago my grandmother was dying of old age. She didn't have any specific disease or diagnosis. She was just 92 and her body was shutting down. Whenever she was hospitalized for general organ failure they would give her a blood infusion and she would rebound.
Yes, everyone in the family made the same grim vampire jokes.
No one asked for her to receive this treatment, and she was definitely not well off financially. Her treatment was entirely driven by the medical staff. The only money being collected was through Medicare.
In retrospect, I'm more than half-way wondering if they were collecting data.
The current zeitgeist is using young pig plasma (no antigens for rejection), so if that pans out, less vampire dystopia, more bacon... Eventually they'll isolate the needed factors, and it'll be an x-monthly shot, and then a pill.