While suffering from the virus, Prince William stuck to his royal engagements throughout the month of April, which included 14 telephone and video call engagements.
Although he kept to his commitments, William, 38, did have a difficult time with the virus.
Despite him being young and healthy, he even "was struggling to breathe" at points.
A source told The Sun, "William was hit pretty hard by the virus - it really knocked him for six. At one stage he was struggling to breathe, so obviously everyone around him was pretty panicked."
The insider continued, "After seeing medics and testing positive - which was obviously quite a shock given how fit and healthy he is - William was determined it should be business as usual though."
The heir to the throne "was determined to fulfill his engagements."
According to the article, William kept the situation private and maintained his busy schedule to assuage worries.
At one event, the paper reports, that William said, "There were important things going on and I didn’t want to worry anyone."