Published online 29 April 2009 | Nature | doi:10.1038/news.2009.416

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A chronology of the H1N1 outbreak.

Swine flu has jumped continents. Associated Press

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.

26 January 2010 : The WHO defends itself against allegations it overhyped the dangers of H1N1 under pressure from vaccine manufacturers at a hearing of the Council of Europe's health committee.

"Let me state clearly for the record. The influenza pandemic policies and responses recommended and taken by WHO were not improperly influenced by the pharmaceutical industry," says Keiji Fukuda.

2 January 2010 : China's ministry of health confirms there have been 659 deaths from H1N1 in the country as of 2 January. A spokesman warns of "the danger of an explosion of outbreaks in some places".

27 December 2009 : The WHO 1230/en/index.html">says over than 208 countries, territories and communities have reported H1N1 cases, including "at least" 12,220 deaths.

8 December 2009 : A review 2/b5106">in the BMJ warns that there is insufficient evidence for or against using neuraminidase inhibitors (Relenza and (Tamiflu) for preventing influenza complications. An accompanying editorial says, "The review and a linked investigation undertaken jointly by the BMJ and Channel 4 News cast doubt not only on the effectiveness and safety of oseltamivir (Tamiflu) but on the system by which drugs are evaluated, regulated, and promoted."

19 November 2009 : China says it has dispatched monitoring teams to 12 regions after a high profile doctor suggested some cases of H1N1 might be being deliberately not reported.

After around 65 million people have been vaccinated, the WHO says H1N1 vaccines appear to have an "excellent safety profile". None of the deaths investigated in those vaccinated have found a direct link to vaccination.

2 November 2009 : Ministry of Health of Ukraine 1103/en/index.html">reports it has recorded over 250,000 cases of influenza-like illness, with 70 deaths.

1 November 2009 : 1106/en/index.html">WHO reports that more than 199 countries and overseas territories have laboratory confirmed cases of H1N1, with over 6,000 recorded deaths.

30 October 2009 : Strategic Advisory Group of Experts (SAGE) on Immunization issues vaccination advice to the WHO, including use of a single dose of vaccine in adults and adolescents and use of any licensed vaccine for pregnant women.

27 October 2009: Russian media reports the country's first H1N1 deaths.

25 October 2009 : This week: vaccinations get underway in many European countries.

18 October 2009 : 1023/en/index.html">This week, Mongolia, Rwanda, and Sao Tome and Principe issue first reports of H1N1 and Iceland, Sudan, and Trinidad and Tobago reported their first deaths.

30 September 2009 : Australia begins mass swine flu vaccinations.

25 September 2009 : European Medicines Agency recommends approval of two H1N1 vaccines, from Novartis and GlaxoSmithKline.

15 September 2009 : FDA approves four H1N1 vaccines, from CSL Limited, MedImmune LLC, Novartis, and Sanofi Pasteur.

10 September 2009 : Two papers published in the New England Journal of Medicine show two new vaccines against H1N1 are likely to be effective after just one dose (paper 1, paper 2).

"The obvious advantage of a one-dose schedule is that, in the current time of vaccine scarcity, it doubles the number of people who may be vaccinated with a fixed amount of vaccine," writes Kathleen Neuzil, of PATH, in an accompanying editorial. "On the basis of these data, it would be appropriate to begin vaccination with the use of one dose of the usual antigen content."

3 September 2009 : Novartis says a trial on 100 subjects shows its H1N1 vaccine is "potentially protective" for 80% of subjects after one dose and over 90% after two doses.

21 August 2009 : Healthy victims of swine flu should not routinely be given antiviral drugs, the World Health Organization useantivirals_20090820/en/index.html">warns.

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 eventId=login">The Lancet (hithardbyswi.html">more on this story).

28 July 2009 : The death of a 22 year old university student in South Africa marks the first death in sub-Saharan Africa. Confirmation of H1N1 as the cause comes 3 August.

22 July 2009 : Two Australian companies say they have started human trials of their swine flu vaccines.

16 July 2009 : WHO changes reporting requirements for H1N1 and abandons issuing global tables with numbers of confirmed cases for all countries.

It surveillance20090710/en/index.html">notes that the increasing number of cases "is making it extremely difficult, if not impossible, for countries to try and confirm them through laboratory testing".

8 July 2009 : WHO antiviralresistance_20090708/en/index.html">says the three incidences of drug resistant H1N1 to date are "sporadic cases" of resistance. "At this time, there is no evidence to indicate the development of widespread antiviral resistance among pandemic H1N1 viruses."

2 July 2009: Japan's health ministry reports that it too has detected a case of Tamiflu resistant H1N1.

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.

29 June 2009: The first case of Tamiflu resistant swine flu has been reported in Denmark

24 June 2009: Argentinian authorities report that a pig at a pig farm in Buenos Aires province has tested positive for the novel H1N1 strain, making it only the second known swine infection outside of Canada.

22 June 2009: Chinese state news source Xinhua reports tests have begun on the first H1N1 vaccine developed in the country.

19 June 2009: South Africa confirms its first case of swine flu - offically marking the disease's spread into sub-Saharan Africa.

14 June 2009: The first swine flu death in Europe has been reported. A woman in Scotland who died with H1N1 had "underlying health conditions", according to the Scottish government.

11 June 2009: Phase 6 has been declared. The world is in a full-blown influenza pandemic for the first time in 41 years.

9 June 2009: The WHO reports that Inuit communities in Canada may be particularly hard-hit. It continues to face questions as to why a full-blown pandemic has not been declared.

8 June 2009: The WHO adds a death in the Dominican Republic to its list, bringing the number of countries that have reported deaths to six.

3 June 2009: H1N1 has reached Africa. The WHO has 0603/en/index.html">confirmed a case in Egypt.

Cases in Australia stand at 501, the largest number outside of the Americas.

A report in Eurosurveillance estimates a reproduction number for the virus — the average number of secondary cases generated by a single primary case — of 2.3 in Japan. That's higher than estimates from elsewhere.

The CDC's Morbidity and Mortality Weekly Report suggests that the outbreak in Mexico may have peaked in late April.

2 June 2009: The WHO says it is 6swineflupandemic_get.html">inching closer to moving its pandemic alert status to phase 6, which would denote official global pandemic status.

1 June 2009: June opens with 17,410 cases reported in 62 countries, including newbies like the Bahamas and Estonia. The death toll in Mexico stands at 97.

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.

27 May 2009: A New England Journal of Medicine article argues, in response to suggestions that the WHO evaluate its criteria for moving to phase 6 and declaring a pandemic, that "the global extent of a pandemic should be described objectively and should be just one factor in decisions about how to respond."

22 May 2009: Australia raises its alert level to 'Contain', even as the Mexican government relaxes its restrictions in Mexico City.

20 May 2009: Worldwide case numbers have passed the scientifically meaningless but impressive sounding 10,000-case mark. Total number: 10,243.

18 May 2009: The day it 0518/en/index.html">confirmed that 8,829 H1N1 cases have been reported in 40 countries, the WHO has cautioned against complacency.

"This virus may have given us a grace period, but we do not know how long this grace period will last," assemblyaddress_20090518/en/index.html">said Margaret Chan, WHO director-general. "No one can say whether this is just the calm before the storm."

However the pandemic alert level is still at five today, one level below a full pandemic.

13 May 2009: As of this morning, 33 countries have reported 5,728 cases of H1N1 to the WHO.

12 May 2009: The CDC cid=mm58d0512a1e">notes that it is seeing some severe complications in cases of H1N1 in pregnant women, including one death in the US.

11 May 2009: The WHO has 0511/en/index.html">confirmed swine flu deaths in Canada and Costa Rica, bringing the total number of countries where fatalities have occurred to four.

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.

8 May 2009: Brazil reports four cases, bringing the number of affected countries to 25. Deaths now stand at 44 worldwide, with 2,500 confirmed cases. Most newly reported cases in new areas, the WHO says, come from travelers returning from affected areas. The CDC reports that hospitalization rates in the US are coming down, to 3.5%, as testing expands to include milder cases.

The Harvard School of Public Health releases a poll in which 83% of Americans polled say they are satisfied with the way public health officials have managed the outbreak. Still, 48% of parents with children in school think they or a family member will come down with H1N1 in the next year.

7 May 2009: Worldwide confirmed cases are now at 2,371.

6 May 2009: WHO 0506d/en/index.html">confirms swine flu cases in Sweden and Guatemala.

5 May 2009: Mexico's H1N1 shutdown should begin to ease tomorrow, with restaurants and cafes set to reopen.

The latest 0505/en/index.html">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.

4 May 2009: Colombia joins the club. There are now 985 cases in 20 countries. Mexico is up to 25 deaths, but officials there say the disease seems to be on the decline.

3 May 2009: Ireland and Italy each report one case. 898 cases are now reported.

2 May 2009: China (Hong Kong special administrative region), Costa Rica, Denmark, France, and the Republic of Korea join the list. Total cases reported to the WHO are now at 658 in 16 countries.

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.

1 May 2009: As of this morning, 331 cases of H1N1 have been reported in 11 countries. According to the 0501/en/index.html">WHO, the worst outbreaks are still in Mexico (156 cases and nine deaths) and the United States (109 cases and one death).

30 April 2009: Austria, Switzerland and the Netherlands join the 0430_a/en/index.html">WHO list of countries with confirmed cases. The agency also announces it will refer to the virus not as swine flu but as influenza A(H1N1).

29 April 2009: The WHO raises pandemic level alert to phase 5, "a strong signal that a pandemic is imminent". First swine-flu death outside Mexico reported as a baby dies in Texas. 161/nn200120/DE/Content/Service/Presse/Pressemitteilungen/2009/082009.html">Germany joins European countries with H1N1 and confirms three swine flu cases. The WHO confirms 7 more cases in Canada, bringing the total number there to 13.

28 April 2009: Seven countries are now reporting 0428/en/index.html">confirmed cases of H1N1 swine flu: the United States, Mexico, Canada, New Zealand, the United Kingdom, Israel and Spain.

27 April 2009: Canada reports six cases of swine flu and Spain reports one. In the United States 40 people have flu confirmed. In Mexico 26 cases are confirmed, with 7 deaths resulting. Estimates for the true number of deaths hover around 80.

The WHO 0427/en/index.html">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.

25 April 2009: WHO director-general, Margaret Chan calls the flu problem "a public health emergency of 0425/en/index.html">international concern ".

23 April 2009: Officials issue orders to close schools in Mexico City, beginning a process of limiting public crowds. Three major soccer [futbol] games around Mexico City close stadium gates to all fans the weekend of April 25-26, with games broadcast on television. Stadium closures continue through May 2-3.

21 April 2009: CDC laboratories confirm two cases in California. Three additional cases confirmed the next day, with two more in Texas added the day after.

28 March 2009: Earliest onset date of swine flu reaching the United States, according to the CDC.

18 March 2009 : Federal District of Mexico 0424/en/index.html">begins to pick up cases of swine flu.