A fourth case of Legionnaires' disease is under investigation in Croydon.
Last month it was announced three patients were being treated at Croydon University Hospital and the cases are being jointly investigated by Public Health England (PHE), Croydon Council and Croydon Health Services.
Laboratory tests have already established that two of the cases have different strains from each other, suggesting there is no link between them.
The fourth case has been identified in a different part of the borough, but it is thought to be a sporadic case with no connections to the earlier three cases.
It is understood the fourth patient is also being treated at Croydon University Hospital.
Legionnaire's disease is a serious lung infection that is caused by bacteria, that can lead to pneumonia.
Initial symptoms include a "flu-like" illness with muscle aches, tiredness, headaches, dry cough and fever.
A spokesman for PHE said they were awaiting further laboratory results on the strain of this case.
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