Bluewater Health is now reporting 15 staff at the hospital have confirmed COVID-19, an increase of four cases from about two weeks ago.
Communications Chief Julia Oosterman said all 15 are currently recovering at home.
"We know from contact tracing, which is a process that is done to go back and see who people were in contact with, that five of those individuals likely acquired the COVID virus in hospital and the remaining 10 likely acquired it in the community."
Oosterman said none of them have recovered as of yet.
"So to be recovered, you have to have two negative swabs done. Some of those individuals are in the process of having had those swabs, so we are hopeful and crossing our fingers that we will be able to report some negative cases soon."
Meanwhile, the number of confirmed cases of COVID-19 locally and recoveries both inched higher on Thursday.
Lambton Public Health updated its site Thursday night to say there are now 183 confirmed cases of the virus and that 90 people have recovered.
No deaths related to the virus have been reported since April 20 and the death toll remains at 14.
There are currently three outbreaks at seniors' facilities in Sarnia, Vision Nursing Home, Sumac Lodge and Landmark Village.
To date, Lambton Public Health has received results from 2,111 tests, of which 91 per cent have been negative.
Bluewater Health reported Thursday morning that 11 people are in hospital with the virus. The hospital said 19 patients are suspected of having it with tests pending, up from six on Wednesday.
-With files from Stephanie Chaves