This may not be exactly epidemic . But I'd have to say in all regard. The biggest problem our world faces today is lack of consciousness to what is around us. lack of awareness and lack of effort put into problems. It is overall the bottom root of every problem we have today in someway or fashion.

If grown men and women would grow more conscious about problems today, If we looked outside and saw the world for what it really is. Saw everything from the violence caused by humans to things caused by nature. If humans became more conscious about the signs of suicide, The signs of lack of education. The deadly effects of drug use and the side effects it brings.Then humans can each understand the reality of life and how things can be better if each human works to fix our problems today.

If humans simply became aware and openly conscious about suicide. And what could be done to prevent it. There would never be a single case of suicide led from depression in our world. Bullies would become conscious of their actions before it's too late. Even with things like medical depression. We would become conscious and work together to find a cure for such a thing where they don't suffer from such.

If humans became aware and conscious crimes wouldn't exist. Because people would never need to do such.Would never need to steal anything as people would be conscious of their actions and know it isn't worth it. That there is other ways.

Even things like global warming are still continuing because humans simply don't become aware of the problem and become overall conscious of its existence that if it does exist we will act far too late to save anything.

Humans in general overall over the years have lacked common consciousness to problems around us and even more so lack the action in getting rid of these problems. Instead humans became fixated and concerned on their own personal problems and wants instead of looking at a bigger picture they will regret not looking at.

TL;DR
Humans are sheep.
They don't look at the world in a bigger picture.
We all gonna die.

The world will never be free of problems. When one problem is solved a new one will always pop up. Nothing is black and white and nothing is as easy as "Here's a solution. Let's use it and now everything will be fixed." This is mainly targeted towards global warming. Yes it is a huge problem but we can't simply just stop it. The only way to stop it is if all usage of fossil fuels completely ceased, the things that power your electricity, heat, water, vehicles, machines, and countless other things. "Fixing" global warming would leave to hundreds of more problems.

I get what you're saying and I agree, there are definitely things we can do to mitigate such problems and yet humans are slow at doing so because of personal goals and desires, but the issues that you present will never fully go away. And even if they could, we would just be presented with even more problems and issues.