Senior charge nurse Rosario Walshe leads the team at Ward A31 at Forth Valley Royal Hospital in Larbert in the Falkirk Council area and said there has been a "huge spike" in cases recently.
The PA news agency was given access to the 32-bed Covid-19 ward where every bed was taken as hospital referrals have doubled since the first wave.
Ms Walshe believes a combination of family gatherings at Christmas, people ignoring guidelines and the new rapidly-spreading variant is behind the rise.
"I've had patients say to me, 'I wish I had listened, I didn't listen. I didn't really believe it was real,' so that was quite an eye opener," she said.
"The last few weeks have been extremely busy and challenging. It's definitely different to the first wave.
"We've seen a lot more admissions with Covid-related symptoms - we've seen lots of groups of family members admitted with Covid, a lot of young people, which you didn't see so much in the first wave.
"We've had some extremely sick people. Patients discussed with ITU (intensive treatment unit), some transferred to ITU. It's definitely been a lot more challenging."
"The reasons for it getting worse I think I can only assume that people weren't following the guidelines.
"We've seen a huge spike in our cases, so I think we can all assume that family get-togethers at Christmas are one of the reasons our cases have gone up so much.
"It does annoy me slightly, lots of staff members are adhering to the policies and guidelines, trying really hard to socially distance and then you've got people who refuse to believe this is real. We still have the element of people that don't believe."
She said some patients had family members die on the ward and in other wards, which was "harrowing" for staff to deal with.
"It's just the way it's so random - you can look fine one minute and be really ill the next, or vice versa. It's just so unpredictable and people can become very ill very quickly," she added.
Ms Walshe said the staff are a very strong team and try to keep each other's spirits up, adding that student nurses have risen to the challenge despite starting their careers at a frightening time.
Among thank you posters and rainbows on the ward is a remembrance tree mural started by the staff during the first wave, with leaves representing each patient - green for those who recovered and returned home and amber for those who died.
"We wanted to acknowledge people - it's something we'd never encountered before and we wanted something to remember them by," Ms Walshe said.
Juliette Murray, deputy medical director for acute services at NHS Forth Valley, said staff have been "amazing".
"We're seeing twice the number of referrals that we saw in the first wave, with all the other pressures, so it's just a bit of a juggling act trying to keep everything going," she said.
Yearly winter strain on the service, staff with the virus, attempting to provide as much elective surgery as possible as well as dealing with urgent cancer referrals and A&E admissions all contribute to the extra pressures on top of the second wave.
Ms Murray is optimistic that a corner is being turned, saying: "We're very much hoping that this is us, we're right at the peak, and we won't see more admissions than we are just now because, obviously, the effect of the lockdown is starting to happen.
"We're managing and we're hoping that's us right at the top and things will start to ease off a little bit more for us over the next two or three weeks.
"People have made heroic efforts throughout the NHS and in our communities to cope with this. We're really, really grateful because that's made a massive difference."