A new outbreak of H1N1 in northern Mexico, which left four dead in the past week, originated in the southern United States, the Chihuahua state governor said Monday.
"It has been confirmed that the woman who died in Chihuahua was on a trip from the (US) state of Texas. Also, those infected in Ciudad Juarez were all linked to trips to the United States or contact with US citizens," Cesar Duarte told journalists Monday.
Duarte said that 18 deaths of people suffering from H1N1 flu had been recorded this year in the US border states of Texas and New Mexico, according to information his office received from US authorities.
Mexican authorities have started a vaccination campaign in northern Chihuahua and ruled out the risk of an emergency on a similar scale to 2009, when Mexico raised the first H1N1 alert.
Swine flu - so named because it was first identified in pigs - has killed some 18,500 people since emerging in April 2009, according to the World Health Organization (WHO).
An H1N1 outbreak was also recently detected in Venezuela, where health authorities said 415 people had contracted the virus, and three people with H1N1 had died this year.