MOSCOW. May 4 (Interfax) - The risk of swine flu cases breaking out in Russia still persists, the Russian office of the World Health Organization (WHO) said.

"True, the risk of infection persists," international medical and sanitary program coordinator at the WHO Russian office Sergei Yeryomin told Interfax on Monday.

Russian doctors should not only monitor passengers arriving from foreign countries which have reported swine flu cases, but also start epidemiological observations, he said.

"Efforts cannot be limited to border screening. We must be prepared for swine flu cases in Russia or on territories of other states. Certainly, the risk remains," Yeryomin said.

Russian health authorities are screening all planes arriving from North and South America, where most of the swine flu cases have been reported. Passengers arriving via other regions are being screened as well.

The passengers have their temperature measured. If they run a fever, they are brought to hospital for A/H1N1 tests. A number of passengers hospitalized in Moscow have proven to be A/H1N1 negative.