"Be infested with" is a phrase that signifies the unwelcome presence of a large number of something, typically pests or parasites. To describe this situation, several synonyms can be used, such as overrun, swarmed, inundated, plagued, besieged, and infested. The word "overrun" implies an excessive number of something overwhelming an area or population. "Swarmed" denotes an aggressive, rapid, and massive influx of creatures. "Inundated" signifies an overwhelming and uncontrollable flood of pests or parasites. "Plagued" and "besieged" both represent the persistence and harm caused by the infestation. In summary, there are multiple verbs that can be used instead of "be infested with" to describe similar situations of unwanted intruders.