In the monsoons the air is very humid , moist and warm – the perfect atmosphere for fungi and molds to grow. Fungi and molds not only leave behind an annoying smell but can be effect the health, they can cause breathing problems and allergies. So when I leave the room for two three days closed, it's a perfect environment to fungus. So when I back it's really hard to stay in the room due to the annoying smell. I need any solution which helps to avoid fungus.
First of all, if humidity is a recurrent problem, you might want to consider investing in a dehumidifier, some might seem costly but they are really worth it, I bought one for 75 dollars for my parents' house, the ambience has improved so much and my mom's health as well(as you mention, the constant humidity made my mom sick, she had fungus stored in her lungs and it took at least 5 months for her to be back at 100% health)
So I can tell you how beneficial would a dehumidifier will be for you, the first couple of weeks you might have to use it on a daily basis, since humidity percentage is going to be at a high percentage. But afterwards, you'll only have to use it 1 to 3 times per week to keep it at the level you want.
Now for the current fungi and mold in your house, make a weak to mild mix of water with bleach, and scrub away. It's a tedious task, but beneficial in the long run.