More details are emerging this evening about the deaths of six elderly patients at the Nazareth House nursing home in Fahan.
Five of the deaths occurred in a cluster in the last five days - it's thought these may have been the result of a respiratory-type illness.
All of the people who died were aged over eighty.
Of the remaining 39 residents at the nursing home - 27 are reported to be showing respiratory symptoms and are being treated with anti-viral drugs.
Their condition is not said to be critical, but visitor restrictions are in place.
North West Director of Public Health Dr Peter Wright, says health authorities are closely managing and monitoring the situation.
The HSE has requested that GPs report unusual clusters of respiratory illness, and blood samples from the patients have been sent to the National Viral Reference Laboratory.
Dr Darina O'Flanagan is Director of the Health Protection Surveillance Centre............