Just a question of time before a virus mutates to take out most of the world's population. That usually happens when a species becomes too crowded. It has been covered in many shows, including the current The Walking Dead. One reason I am not buying a new car. In the post-zombie world, diesels are more likely to keep operable, though once the batteries run out we'll need to have kick-start motorcycles. I have seen cord-start diesel motorcycles people fab'ed on youtube.