Two London Jewish schools have suspected cases of swine flu.
A boy at JFS whose sister was diagnosed with the virus last week is being tested for the virus but the results of the test have not been disclosed.
Kerem House Nursery in Hampstead Garden Suburb has also had a swine flu scare when a number of staff members were taken ill and the school has been closed since Monday until reopening yesterday.
JFS said the school "is taking and following the regular advice from both the local authority and the area health authority".
"It is understandable that parents and carers are concerned but the situation is under control. Official medical advice is that the symptoms are mild in the majority of cases.."
He added: "Schools are staying open because the virus is spreading in the wider community through mixing with family and close friends outside of school.."
Brent Council confirmed 31 schools in the borough have suspected or confirmed cases of swine flu but added that the number was changing all the time.
Vice Chairman of Governors for Kerem House Nursery, Joe Stelzer spoke to parents on Tuesday after the nursery closed.
Mr Stelzer said: "Primarily, the closure was because our staffing resource fell short of the minimum requirements required due to several staff being ill. We were concerned that they might have swine flu but, as I am sure you are aware, swabbing is not now being carried out. They are now fit to work.
"We fully expect there to be more cases both at Kerem House and Kerem School as there are numerous instances within local families."