There have been no laboratory-confirmed cases of swine flu in South Africa, the National Institute for Communicable Diseases (NICD) said on Monday.

"The laboratory results on the one suspected case from the Western Cape province are negative," said the NICD deputy director Dr Lucille Blumberg.

"The person has recovered fully and there are no secondary cases."

Susan Kok, 58, from the Western Cape, had flu-like symptoms when she returned from a month-long holiday in Mexico with her husband.

Blumberg said her case would remain a suspected one as the specimen taken - a swab from her throat - was of an inadequate quality to be properly assessed.

A woman from Gauteng who was suspected of carrying swine flu after visiting Mexico tested negative for the disease last week.

Meanwhile on Monday, The Star newspaper reported that a South African couple, Mari and Faghmi Abrahams, was amongst 300 people placed under an eight-day quarantine in a Hong Kong hotel.

This was after a person from Mexico staying at the hotel was confirmed to have contracted swine flu. He was in a stable condition.

The couple's quarantine began on Friday and they would be able to fly back to South Africa on May 10.

Agence France Press reported that the World Health Organisation had put the number of confirmed deaths from swine flu at 25, all but one of them from Mexico.

"Twenty-one countries have confirmed cases of the virus which has affected around 900 people," AFP said.

Symptoms of the virus included fever, body aches, a runny nose, sore throat, nausea, vomiting and diarrhoea.

A thermal image detection system which could help detect people carrying swine flu had been installed at Lanseria airport, and two similar machines would soon be in place at OR Tambo airport in Johannesburg.

Health officials in South Africa have urged people to adhere to common sense hygienic practices such as frequently washing their hands and putting their hands over their mouths when coughing or sneezing.