Mexico has seen almost 170 deaths from suspected swine flu
Eight people in Wales have been given the all-clear after being tested for swine flu.
A further 19 people in Wales are still being investigated but there are no confirmed cases, said health officials.
All those being tested have displayed mild symptoms following travel to Mexico or the USA.
An advertising campaign urging people to follow basic hygiene advice has been launched to help prevent the spread of swine flu.
There are five confirmed cases in the UK, including a girl of 12, but all are responding well to treatment.
Almost 170 deaths from suspected swine flu have been reported in Mexico.
Chief Medical Officer for Wales Dr Tony Jewell said the Welsh Assembly Government was liaising with health bodies and colleagues around the world to monitor the situation.
"We fully expect that there will be cases reported in Wales, but reiterate that we have no confirmed cases as of yet," he said.
Cover your nose and mouth when coughing or sneezing, using a tissue where possible
Dispose of tissues promptly and carefully
Wash hands frequently with soap and water
Clean hard surfaces such as door handles regularly with a normal cleaning product
Help your children to follow hygiene advice
Source: National Public Health Service for Wales/Welsh Assembly Government
"Although it is natural for people to feel apprehensive, we reassure the public that we are working to prepare for the arrival of the virus, have been for many years, and have robust procedures in place."
He said a successful exercise was held in Wales only last week to rehearse for an outbreak of this nature.
A Department of Health campaign was launched on Thursday to help prevent the spread of swine flu.
"Measures to prevent spread of infection can be taken by the public such as regular hand washing, covering your mouth when coughing or sneezing, using a tissue when possible, disposing of tissues quickly and carefully, and helping your children follow this advice," said Dr Jewell.
"If you have returned from an affected area and have flu-like symptoms, stay at home, call your GP or NHS Direct and you will be assessed and receive treatment if necessary."
• Members of the public can call 0800 1513513 for recorded information about swine flu