The Morningside Medi-Clinic nursing sister being treated for an arena virus is still in a serious but stable condition, the clinic's spokesperson said on Wednesday.

Melinda Pelser said that the list of the 94 people being monitored for signs of the virus might drop on Thursday as the window period for people who came into contact with a paramedic who died from the virus, expires.

The nursing sister was admitted earlier in October after developing symptoms of the virus which is believed to have caused the deaths of three other people treated at the clinic.

It was first detected after a paramedic and another nursing sister died after coming into contact with a woman flown in from Zambia for treatment for what was initially thought to have been tick bite fever.

Colleagues hope the nursing sister will take a turn for the better soon.

Sapa