Three people have died following cases of an infectious disease in Johannesburg, the health department said on Sunday.

"We are on high alert following the confirmation of three cases of an unknown highly infectious disease which has since led to three deaths," said the department in a statement.

According to the department the first patient was a female from Zambia who was critically ill when she arrived on 12 September in South Africa.

She was treated for tick-bite fever and other potential infections at Morningside Medi-Clinic.

"Two days later she died. Blood samples were taken and the results were not conclusive of any particular disease including the Viral Hemorrhagic fevers."

The second patient, was a Zambian male paramedic who had accompanied the first patient.

He was admitted on the 27 September at the same facility with flu-like symptoms and treated for a variety of infections.

"His condition initially improved but later deteriorated on Wednesday, October 1 and he died the following day."

Investigations for viral hemorrhagic fever and other formidable infectious diseases were conducted and the results came out negative.

A nurse at Morningside Medi-clinic who came into contact with the first patient became ill with flu-like symptoms and was subsequently admitted to Sir Albert Robinson hospital in the West-Rand on Wednesday.

"Her condition deteriorated on Saturday and she passed away today (Sunday). Viral hemorrhagic fever and other formidable infectious diseases were negative."

According to the department, systems were in place to follow-up on everyone with which the deceased had contact.

Healthcare workers and family members were being monitored for raised temperatures and flu-like symptoms for a period of 21 days.

"Steve Biko Academic and Charlotte Maxeke Academic hospitals are on high alert and ready to handle any cases related to this situation."

Members of the community with travel history to Zambia during the last month and who suffer from raised temperatures or flu-like symptoms were requested to report to the nearest health facility for a medical examination or contact Dr Chika Asomugha on 082 330 1490.

Sapa