Mikva’ot in Israel follow extensive regulations to ensure that they are hygienic, and these should suffice even now.
Since these regulations are linked to the volume of mikveh usage, they tend to balance out. A mikveh in a big city might actually disinfect and switch the water more frequently than one in a smaller community.
If your immune system is compromised, or if you have a medical condition or are at high risk for any reason, make sure to discuss with your physician whether there are any special precautions you need to take at this time.
Women who are in quarantine for potential exposure to Coronavirus are forbidden to immerse, medically and halachically.