It recommended keeping hydrated, taking painkillers and washing hands thoroughly to prevent the winter vomiting bug from spreading.
The public are urged to stay at home for at least two days until the viral symptoms disappear.
Norovirus symptoms include vomiting, diarrhoea and painful stomach cramps.
“There have been a small number of outbreaks of norovirus, including in south London,” said NHS Choices on Twitter this morning.
“Norovirus is easily spread and there is no cure. Follow these steps to treat yourself or your child at home.
“Stay hydrated, take paracetamol, prevent spread, stay at home for two days after symptoms clear.”
It’s warning came after King’s College Hospital NHS Foundation Trust confirmed it was closing all wards at the Princess Royal University Hospital from visitors, due to a norovirus outbreak.
The Princess Royal University Hospital, Orpington, closed all of its wards to visitors on Tuesday.
A norovirus outbreak in the community and hospital forced the visiting ban, said the NHS trust.
No date has been set for when the wards will re-open to visitors, but people can still visit “extremely unwell” relatives in exceptional circumstances.
Patient safety and wellbeing is the hospital’s number one priority, the trust added.
“We have taken the decision to close all wards to visitors at the Princess Royal University Hospital (PRUH) because of an outbreak of norovirus in the community and some cases in the hospital,” said King’s College Hospital NHS Trust. “We apologise for any inconvenience this may cause.
“Unfortunately, we cannot give a precise date on when we will re-open wards to visitors.
“This depends on the number of cases we are seeing in the hospital, and the prevalence in the local community.
“Our top priority is the safety and wellbeing of all patients so we will permit visiting when there is a low risk of the virus being transmitted.”