"Although the Gauteng province is not a malaria endemic area, there have been cases where the malaria ...infected mosquitoes were imported into the province by people travelling from Malaria endemic areas...," spokesman Simon Zwane said in a statement.
These imported mosquitoes could then infect people with malaria, but conditions in Gauteng did not allow the type of mosquitoes that carry the disease to breed.
Two people diagnosed with malaria, in Eldorado Park and Lenasia two weeks ago, had not travelled to malaria endemic areas, Zwane said.
"The possibility is that they were infected through importation of infected mosquitoes."
Last year, 1700 cases of malaria were reported in Gauteng and 23 people died from the disease.
"It was established that those who [died], were people who did not take precautionary measures against the disease and presented late at health facilities."
Zwane said that people travelling to malaria areas, such as the Kruger National Park, Tanzania and Mozambique, needed to start taking medication to prevent the disease before their journeys. Malaria symptoms include fever, headache, flu-like symptoms, body aches and pains, nausea, vomiting and diarrhoea. Anyone experiencing these symptoms should seek medical help.
The National Institute for Communicable Diseases said that the two Gauteng residents infected with malaria had responded well to treatment.
The institute said that it was very rare for malaria-carrying mosquitoes to survive the journey from their places of origin.