Hospital patients were looked after in corridors and ambulances left queuing outside after a 'sharp rise in admissions' at the Royal Cornwall Hospital.
A visitor to the hospital in Treliske told ITV News she witnessed up to a dozen patients in corridors as she visited a relative on Monday night.
It comes as the Trust confirmed it's seen a sharp rise in admissions after temperatures dropped at the weekend.
Over the weekend the hospital was particularly busy, with waits of more than an hour for the emergency and urgent care departments.
But despite it being very busy the visitor told us:
South Western Ambulance say it did have an "unusual spike in demand" over the weekend.
The Royal Cornwall Hospitals NHS Trust added it was particularly busy and had also seen a spike in emergencies.
The Royal Cornwall Hospitals Trust added: "Together our staff have been working tirelessly to make sure people are treated and return home, or are admitted, as quickly as possible and we are seeing an improvement in the situation."
The Trust has urged people to use the most appropriate place for their needs, and to take prescribed medicines and to seek help early from a GP, or by calling 111, if symptoms are getting worse.
It continued: "Generally we’d ask people to make use of the pharmacies, the brilliant network of minor injury units around the county and the 24 hour urgent treatment centre at West Cornwall Hospital in Penzance."
Opening times and live waiting times are available on the Trust's website, www.royalcornwall.nhs.uk, along with information on how to cope at home with the bugs and minor illnesses.
You can watch the full item on our programme below: