Health officials in South Africa said swine flu, also known as the H1N1 influenza virus, has been ruled out in one of the two suspected cases there.
The deputy director of South Africa's National Institute for Communicable Diseases, Lucille Blumberg, said Thursday a woman in central Gauteng province suspected of carrying the virus has tested negative.
Blumberg said a second patient in the Western Cape is still awaiting her test results, but the throat culture submitted for testing is not considered ideal for reliable lab results. Officials earlier said the sample was not stored properly.
Both women exhibited mild flu-like symptoms after visiting Mexico. Neither woman is seriously ill.
So far, no cases of swine flu have been confirmed in Africa. But officials throughout the continent continue preparing for a possible outbreak.
Scientists said the virus has not reached pandemic proportions, but they are still concerned about the preparedness of poor countries to respond to a crisis.
Governments in many countries, including Rwanda, Nigeria and Ghana, are screening arrivals at airports and other points of entry, watching for anyone coming from an affected country with possible flu symptoms.
Kenya, Uganda and other countries said they have stockpiled doses of the anti-viral drug Tamiflu, which can be used to treat influenza symptoms.
West African countries have reactivated early warning systems established following the outbreak of avian flu three years ago.
African health officials met in Ethiopia this week to discuss how to counter a possible pandemic. The conference was planned months ago, but it took on new urgency since the global spread of the swine flu virus.
Some information for this report was provided by AFP.