Staff absence levels hovered between 200 and 250 per day at the start of December - but latest figures obtained by the Chronicle show that 625 employees were off work on January 6.
So far this month, an average of 520 staff each day have been on sick leave through self-isolation or illness.
The town’s infection rate is now 2,607.3 per 100,000 residents, with more than 6,400 people testing positive for Covid in the last seven days - a 550 per cent increase since before Christmas.
Almost 4,000 patients have been admitted to the hospital with the virus since the start of the pandemic, and the Chronicle understands figures are continuing to rise quickly,
Latest data shows there are 73 people in Barnsley Hospital with Covid-19 - almost four times the figure on Christmas Day.
Barnsley Central MP Dan Jarvis said: “Covid hospitalisations are increasing at an unprecedented rate and this means our NHS services are under immense pressure.
“The number of Covid patients in hospital is now at its highest level since the pandemic began, and over 12 per cent of our NHS workers are either isolating or on sick leave, which is having a severe impact.
“Testing is not only key to reducing the spread of the virus, but it also helps ensure our frontline workers can keep services running and continue their extraordinarily important work.
“NHS staff, emergency services, care workers and key workers are yet again going above and beyond, often with limited staff and resources.
“The best thing we can do to support their herculean efforts is to get our vaccine and booster jabs.”
More people than ever are taking a PCR test in the town - and the proportion of those receiving a positive result is also at an all-time high.
A total of 46.3 per cent of tests are returning a Covid-positive result.
A hospital spokesperson said: “Like others across the country, we have seen an increase in the number of patients with Covid-19 over recent weeks.
“Numbers of in-hospital cases reflect Barnsley’s high community prevalence of Covid.
“Alongside this, there has been an increase in Covid-related staff absence.
“However, the trust has been working through our robust contingency plans to maintain safe services for our patients, such as supporting the timely discharge of those who are well enough to leave hospital.
“Our staff are working incredibly hard alongside healthcare partners and we thank them for once again responding to this latest surge in demand./
“We also ask the Barnsley public to continue to work together as a community to limit the spread of this virus.”
Public health director Julia Burrows said the town is seeing a lower proportion of people with severe illness, something she attributes to high vaccination uptake rates.
“Just like the national picture, Barnsley case rates have climbed steeply since Christmas, reaching close to triple those of previous peaks during the pandemic,” she added.
“Due to the very high number of people with Covid-19 in Barnsley, the number in hospital who are positive for Covid-19 has also risen, as experienced across the country.
“However, with the very good vaccine uptake in Barnsley, including for the booster dose, we are seeing a lower proportion of cases with severe Covid illness needing hospital treatment compared to before the vaccine was available, particularly in those who are fully vaccinated with three doses.”