While the weather must definitely be accounted for, running is still possible, even when it's cold, dark and rainy. You just have to get yourself outside.
While health and distancing measures will be effective in controlling both of these illnesses, you can expect some extra stress due to the similarity of these conditions.
The closure of gyms during quarantine robbed many people of their motivation to move and stay active. Here are some ways to regain your post-lockdown fitness level.