Timeline: Swine flu

A chronology of the H1N1 outbreak.

A new strain of swine flu - influenza A (H1N1) - is spreading around the globe. This timeline will be continually updated with key dates, drawing on authoritative information from the World Health Organization (WHO), the US Centers for Disease Control and Prevention (CDC) and other sources. For more on the situation see the Nature News swine flu special, and read updates on The Great Beyond blog.

3 August 2009 : India confirms first death from H1N1, the victim being a 14-year old girl in the city of Pune.

29 July 2009 : Researchers from the US Centers for Disease Control and Prevention warn that pregnant women "might be at increased risk for complications from pandemic H1N1" in a research paper in The Lancet (more on this story).

The UK moves its swine flu response from 'containment' to 'treatment'. "Our national focus should be on treating the increasing numbers affected by swine flu," says health minister Andy Burnham. In the US there are or have been cases in all 50 states, including 17 deaths, according to the CDC. MedImmune, a biotechnology firm in Gaithersburg, Maryland, wins a $90 million contract from the federal government to begin developing a live attenuated vaccine for H1N1. "This virus may have given us a grace period, but we do not know how long this grace period will last," said Margaret Chan, WHO director-general. "No one can say whether this is just the calm before the storm."

Mexico has reported 48 deaths and the United States three. Worldwide, 30 countries have officially reported 4694 cases. A modeling study in Science suggests that the virus spreads at a rate comparable to that of previous influenza pandemics. The latest WHO figures say the virus has now spread to 21 countries. Mexico has reported 590 cases and 25 deaths while the United States has reported 286 cases and one death.

However, the Texas Department of State Health Services has confirmed a second person has died in the United States. The DSHS says a woman with "chronic underlying health conditions" died earlier this week.

The following countries have reported cases but no deaths: Austria, Canada, China (Hong Kong Special Administrative Region), Costa Rica, Colombia, Denmark, El Salvador, France, Germany, Ireland, Israel, Italy, Netherlands, New Zealand, Portugal, Republic of Korea, Spain, Switzerland and the United Kingdom.

Canadian authorities announce that H1N1 has been detected in a swine herd in Alberta. The pigs likely caught the virus from a Canadian who had recently visited Mexico, making this the first known case of human-to-animal transmission.

The WHO raises pandemic alert level to 4 having confirmed human-to-human transmission able to cause 'community-level outbreaks'. "Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion," says the organisation.