The 23-year-old said he initially thought he had a chest infection, but claims the illness has got “f***ing worse”.
Niall originally wrote on Twitter: : “Get a chest infection Christmas week… cool cool cool…. Not ideal.”
Fellow singer, Five Seconds of Summer star Ashton Irwin cheekiy claimed Niall had got the illness from him, claiming the pair had locked lips.
“I thought it was a chest infection and it’s not, it’s f***ing worse”
He wrote to the star saying: “Me too man, we shouldn’t of kissed. I was highly contagious.”
Niall played a long with the joke replying: “You really shouldn’t have. Ruined my Christmas.”
He later followed up the comment, adding: “I thought it was a chest infection and it’s not, it’s f***ing worse.”
However, things then escalated, when Niall tweeted: “Should have listened to my mother years ago when she said ‘Don’t go out with wet hair or you’ll get pneumonia’.”
Concerned fans started worrying over his health straight away.
One wrote: “Don’t get pneumonia.”
Another added: “HAVE YOU GOT PNEUMONIA???”
A third commented: “We hope you’re well. Take care, please.”
Get better soon Niall.