The World Organisation for Animal Health (OIE) said testing was under way on the A/H1N1 virus, which has been renamed from swine flu.
"Information available to the OIE does not indicate, at this time, that the influenza outbreak currently occurring in the United States and Mexico was preceded by an outbreak of swine influenza," it said in a statement.
"Within a few days, scientific investigations that are currently under way should indicate if the virus circulating in humans is capable of infecting animal species, such as pigs, chickens and horses.
"It is not correct to call the current disease 'swine influenza'. The virus that is circulating includes genetic components of human, avian and swine origin.
"The OIE proposed to refer to this new virus as 'North American influenza', using the same approach to nomenclature as used with the Asian influenza and Spanish influenza outbreaks that have occurred in the past.
"Given there is no case of infection in animals confirmed in the zones where cases of human infection have been detected, it is not necessary to introduce specific measures for international trade in swine or their products nor to consider that consumers of pork products are at risk of infection."
The OIE says it will continue to respond to new, incoming information as the situation evolves.
Two days ago, the OIE director general Bernard Vallat called for scientific research to be started with urgency to help clarify the sources and the risks presented by the virus to veterinary public health and to the different animal species, notably pigs, poultry and horses.