Vilnius - Lithuania's health authorities were awaiting the results of tests Thursday in what could be the first case of swine flu in the Baltic states.

Samples taken from a Lithuanian citizen who returned to the country from Mexico on April 23 have been confirmed as containing a Type A influenza virus.

The samples have been sent to specialist laboratories in Britain to confirm whether it is swine flu, the Lithuanian Health Ministry said.

"We have a message from London that results will be available as soon as possible, maybe on Friday evening," Health Ministry spokesperson Giedre Maksimaityte told the German Press Agency dpa.

The possible victim, who is male and around 38 years of age, felt unwell with flu-like symptoms on April 25 and submitted himself to tests on April 28. He was said to be in good health at present and is being kept in isolation in a Vilnius hospital.

"His wife was checked today and she doesn't have any virus," Maksimaityte said.

The man's route back to Lithuania from Mexico included stops in Prague and Amsterdam, dpa learned, but efforts to contact his fellow passengers would not be made until the results of the tests were available, Maksimaityte said.

Lithuanian pharmacies have reported a surge in sales of anti-viral drugs in recent days despite official advice that they would be ineffective in the treatment of swine flu.

Late Wednesday the World Health Organization upgraded the status of the swine flu virus' spread to grade five out of six, indicating that a global pandemic is thought to be "imminent."

WHO's representative in Lithuania, Robertas Petkeviciaus, said his organization was doing everything possible to combat the spread of swine flu.

"The United Nations has announced that a pandemic is inevitable, but the world has never been so well prepared as it is now," he said.