I also have a problem with "viruses" that set me back, but recently I started to think it may not be viruses I pick up. It's more likely something that got into me from the beginning and it comes out to reproduce when conditions are right. Yes a cold can trigger that, as others I get over it but don't feel alright for sometime. I think the cold weakens my defenses allowing the "other thing" come out taking advantage of my weakness. I'm now looking into worms and parasite, rather than viruses, as I've noticed that symptoms are sometimes worse between the new and the full moon, which some say to be typical of parasites, but that could just be a coincidence. Jenny, if it's 30 patients then it can certainly give some good indications, but still remain unconvinced regarding possible long-term effects in respect of stealth infections.