Ah yes but what about dry Pneumonia? Dry Pneumonia is where your lungs produce mucus cause you inhaled particulates of dry matter. Dry Pneumonia killed many people during the Dust Bowl period of time here in the US. The point is that even the weakest viral infection can damage  your immune system enough to cause another viral to come in which is stronger than the last one. Though, anti-viral medicines also damage your immune system on their own so yeah. Without the medical supplies we have now, medical care would basically be set back to the 1800s maybe 1900s. Mortality rates would be through the roof after the first winter even if you are use to living in the cold. We are use to having all the food we could possibly ever want in the winter seasons now but when we can't produce said food what is going to happen? Most people'll die from lack of food rather than disease in the first year. It is the children born afterwards that would be the issue not our generation. They would have trouble fighting off even the easiest disease we have now.