I don’t think the game models infection transmission. Instead, colds are contracted as a result of poor health. I’m not sure about 0.F-3, but somewhere in the 0.F cycle the health stat logic was revamped and earlier strategies thrown out the window.
Currently a poor health stat is a sure way to get a cold, and it’s a pain to turn a tanked stat around as it takes a long time to just turn the plummeting stat around to start to slowly inch its way up again.
It used to be almost free points to start as an XXXL character and then starve yourself down to a healthy weight over a number of weeks, but that’s now very tricky due to the health dump resulting in getting constant colds. In principle it ought to be possible to manage it by eating appropriate vitamins without calories, but you typically don’t have vitamins available. Also, junk food aversion is now essentially free, as junk food is extremely harmful to your health stat (I wouldn’t be surprised if drinking bleach is less harmful), so you can’t eat it anyway.
Note, though, that I don’t know when these changes were made in relation to 0.F-3: it might have been later.
I’ve had that happen as well. I’d strongly recommend eating enough vitamin rich food to provide that health benefit, while not eating enough calories to stave off weight loss. That’s what I’d try if I’m going for XXXL again. That would mean it takes a lot longer to reach normal weight, but it’s both more realistic and a less punishing route.
However, I think the UI has improved to provide some feedback regarding vitamins since 0.F-3, so you may be out of luck in that department.
I wouldn’t be surprised if you’d get two or three additional colds during your way back from the bottom of the health pit. I think it took a week or even two for my character to turn things around (i.e. not trying to push through the health bottom, but rather actually slowly improve) when junk food turned deadly (I didn’t know things were off before I’d already hit the bottom), so that’s from being at the bottom trying to push through it and switching to a supposedly healthy diet (beware those deadly salted peanuts, but unsalted are healthy and good for you).
The junk food property seems to add on top of whatever health effect the food is marked as, rather than included in it. However, that’s based on my extreme experience of being hit by the transition and its effects, rather than having investigated exactly what the effects are calculated as.
Before the transition I had my character freely eat any junk food that wasn’t marked as harmful, assuming not being junk food intolerant would mean the regular indications were valid. After the transition I only looked into it when my character was at the pit of the health well when trying to find out why it suddenly was hit by all kinds of ill effects. As far as I can tell, there were no other factors influencing the health during that time.
Yes, the bug that caused the trend not to be reset was active at the time, but that wouldn’t have been a problem in my case if there wasn’t a hidden negative health effect to amplify. The bug just caused it to take a lot longer to turn things around once “healthy” junk food was no longer eaten.