According to experts, many people are turning up for work even if they are ill as they fear they might get sacked.
They also warned that this issue of "presenteeism" might lead to a possible increase in mental health problems.
"Not only can illnesses be passed on to other colleagues, but ill employees are likely to work less effectively, being more prone to costly mistakes and taking longer to recover," the Mirror quoted researcher Dr Jill Miller as saying.
A fall in absences on average from around eight days a year to less than seven was matched by a third of bosses reporting a rise in staff turning up ill, said her report for The Chartered Institute of Personnel and Development.
The study of 700 firms also found stress and mental health issues were growing.
Dr Miller said if bosses failed to tackle the issues, work-related illness would become more serious.
"Increasing workloads and worries about job security could contribute to stress and mental health being two big causes of long-term absence from work," warned Helen Dickinson, of the healthcare firm Simplyhealth.