The nursing sister being treated for an arena virus is still in a serious condition at the Morningside Medi Clinic, a spokesperson said on Monday.

"She is still serious, but stable," said Melinda Pelser.

She was admitted earlier in October after developing symptoms of the virus which has been linked to the deaths of three other people treated at the clinic.

A paramedic and another nursing sister are believed to have contracted it initially from a South African woman flown in from Zambia with what was initially thought to have been tick bite fever.

Pelser said 94 people who may have come into contact with the three are still being monitored but so far nobody else has been admitted.

If anyone shows a change in temperature they will be brought into the hospital for closer monitoring.

The arena virus causes a type of haemorrhagic fever and is associated with small rodents.

A Gauteng health department task team declared the hospital safe for patients, visitors and medical procedures last week, after endorsing its infection control procedures.

Sapa