No, intermittent fasting does not make you more susceptible to diseases. On the contrary, studies show that intermittent fasting strengthens your immune system. Right now it is all about making healthy decisions. And this definitely includes intermittent fasting.
You should only take care to avoid longer fasting periods (>24h) during the coronavirus outbreak in order not to expose your body to additional stress. If you also consume little sugar and processed products and ensure sufficient relaxation, you will do only good to yourself and your health.