World Health Organization declares A (H1N1) influenza pandemic

BMJ 2009; 338 doi: (Published 12 June 2009) Cite this as: BMJ 2009;338:b2425
  1. John Zarocostas
  1. 1Geneva

    The head of the World Health Organization has declared the first influenza pandemic in 41 years after intense consultations with top officials from countries that are experiencing rapid transmission of the novel A (H1N1) flu virus at the community level, and with international experts monitoring the global outbreak.

    “The world is now at the start of the 2009 influenza pandemic. We are at the earliest days of the pandemic,” Margaret Chan, WHO director general, told a news conference, shortly after she decided to raise the level of influenza pandemic alert from phase 5 to the maximum, phase 6.

    “We have reason to believe that this pandemic, at least in its early days, will be of moderate severity,” she said and noted “the virus is contagious, spreading easily from one person to another and from one country to another.”

    Dr Chan took the decision after a conference call on Wednesday with health officials from the eight most affected countries—the United States, Mexico, Canada, the United Kingdom, Spain, Australia, Japan and Chile—followed by a meeting on 11 June with the emergency committee of international experts.

    Countries are already experiencing widespread transmission, as in the case of the US, she said. “We need to give them the space and flexibility to recalibrate public health response.”

    But she also emphasised that WHO did not wish to provide one set of guidance for all countries.

    Meanwhile, the US secretary for health and human services, Kathleen Sebelius, said that today’s decision by WHO was expected. It “doesn’t change what we have been doing here in the United States to prepare for and respond to this public health challenge.”

    Dr Chan, a pandemic specialist, said that the spread of the virus in several countries “can no longer be traced to clearly defined chains of human to human transmission. Further spread is considered inevitable.”

    As of 11 June, a total of 28 774 laboratory confirmed cases, including 144 deaths, have been reported by 74 countries to the global health agency.

    Australia has reported 1307 cases and no deaths, Canada 2446 and four deaths, Mexico 6241 cases and 108 deaths, and the United States 13 217 cases and 27 deaths.

    Other nations that have reported large numbers of confirmed cases include Chile, with 1694 cases and two deaths; Japan, with 518 cases; the United Kingdom, with 822; Spain, with 357; Argentina, with 256; Panama, with 221; and China, with 174.

    So far, in all areas with large sustained outbreaks, which have largely occurred in people younger than 25, about 2% of cases have developed into severe illness, often with rapid deterioration to life threatening pneumonia, Dr Chan said.

    Moreover, most of the fatal infections reported have been in adults between the ages of 30 and 50 years, noticably different from epidemics of seasonal influenza, where deaths are mainly in frail elderly people, she said.

    She added that all countries “should prepare to see cases, or the further spread of cases, in the near future. Countries where outbreaks have peaked should prepare for a second wave of infection.”

    She also said that WHO continued to recommend no closure of borders, no restrictions on travel, and no trade bans.

    Similarly, Ban Ki-moon, the United Nations secretary general, said in a statement on the pandemic in New York on Thursday, “We must guard against rash and discriminatory action, such as travel bans or trade restrictions. Our response to any pandemic must be grounded in science.”

    But Mr Ban also noted that so far the virus has affected mainly developed countries but added that that was likely to change, and that would have consequences.

    “Poorer countries have less developed health systems. People tend to seek health care later. And there is often a higher level of other diseases in the general population,” he said.

    In a similar vein, Dr Chan said, “Perhaps the greatest concern [is that] we do not know how this virus will behave under conditions typically found in the developing world.”

    “Although the pandemic appears to have moderate severity in comparatively well-off countries, it is prudent to anticipate a bleaker picture as the virus spreads to areas with limited resources, poor health care, and a high prevalence of underlying medical problems.”

    Marie-Paule Kieny, director of WHO’s initiative on vaccine research, said that the agency expected a quick increase in production of H1N1 influenza vaccine by manufacturers and to have the first doses in September.

    Dr Kieny said that when the agency has enough evidence it will also make a recommendation as to which groups should be prioritised for the first doses of the vaccine.

    Limited preliminary data indicate that severe cases have occurred in people with chronic conditions, including respiratory diseases, notably asthma; cardiovascular diseases; diabetes; autoimmune disorders; and obesity. Pregnant women are also at increased risk of complications, Dr Chan said.

    Production of antiviral drugs, which have proved effective in fighting the virus, is also being increased, WHO officials said.

    Dr Chan said that a donation of five million courses of the antiviral oseltamivir (Tamiflu) by the Roche group has been dispersed to 121 countries. She expected to receive a second donation of 5.6 million doses, part of which would be in paediatric formulation, which would be distributed worldwide so that countries would have something on hand to deal with the situation.


    Cite this as: BMJ 2009;338:b2425