A neighbour of the factory were three workers have been diagnosed with Legionnaires’ disease cases has become the fourth suspected case.
Watchdog Public Health England (PHE) has confirmed the suspected case has been identified as part of ongoing investigation at Faltec Ltd in Boldon.
The agency said evidence suggests the latest suspected case had “acquired the infection” before control measures were put in place at the factory during the weekend of May 17.
This patient required hospital treatment but has since been discharged and is recovering at home.
The first three confirmed cases are people who have worked on the Faltec site and the fourth is a resident whose garden overlooks the factory boundary.
Dr Tricia Cresswell of the North East PHE Centre said: “We are working closely with South Tyneside Council and the HSE to investigate potential sources of infection and the company is co-operating fully with the investigation.
“On the advice of the Health and Safety Executive, a range of actions have already been taken by the company to treat and disinfect possible sources of the infection, including cooling towers and other water systems.
“Legionnaires’ disease does not spread from person to person and can only be contracted from the source of the contaminated water.
“Due to the incubation period of Legionnaires’ disease, it is believed that the people who have been ill were all exposed to the legionella bacteria before control action was taken by the company.
“As a precaution staff have been advised to contact their GP if they develop a chest infection or other respiratory symptoms.”
Chris Gillies, principal inspector from the Health and Safety Executive, said: “Following our on-site investigations, we have served a enforcement notice on Faltec Ltd requiring improvements in the management of water safety systems to further reduce the risk of future cases of Legionnaires’ disease.
“We will be monitoring the site and ensuring that the company complies with the requirements of the notice.”
Amanda Healy, director of Public Health for South Tyneside Council, said: “Our first priority is to protect the health of factory workers and local residents.
“We are not aware of any new cases infected since the factory took action to treat and disinfect water sources, but we are continuing to work closely with HSE and PHE to confirm and control any possible sources of infection on the factory site.”
Dr Cresswell added: “In addition to the notice served by HSE, I have written to Faltec Ltd emphasising the importance of water safety practices in protecting factory staff and local residents. Any local residents who develop a chest infection or other respiratory symptoms should contact their GP in the usual way.”