AFP reports: 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. 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).