Influenza News, Developments and Selected Scientific Publications, January 21st 2010

ECDC comment

Influenza News, Developments and Selected Scientific Publications, January 21st 2010


It has been suggested by some politicians that the World Health Organization (WHO) was influenced by the pharmaceutical industry in its handling of the 2009 pandemic. The issue will be debated in the Council of Europe in the week beginning January 25th.  In this Press Conference Dr Fukuda convincingly answered four questions relating to this topic. These were: whether the 2009 influenza A(H1N1) pandemic has been a real pandemic, whether WHO changed its definition of the pandemic, whether WHO overplayed the pandemic and whether WHO in any way was unduly influenced by industry. He explained why the 2009 was a real pandemic and fitted the pre-existing definition of the pandemic which was not changed. He also described WHO’s transparent relationships with industry. 


See ECDC Scientific Advance: Seroepidemiolgy of the 2009 Pandemic in the UK in its Spring- Summer Wave

Efforts to assess the severity of the 2009 pandemic sometimes compare numbers of confirmed deaths with those estimated for seasonal influenza. This short but important note by WHO explains why such comparisons can be misleading. Numbers of deaths for seasonal influenza are only estimates and use statistical models designed to calculate so-called excess mortality that occur during the period when influenza viruses are circulating widely in a given population. In contrast individual deaths confirmed and reported to be due to influenza will only represent a sub-group of the true numbers of deaths.

  • Summary of human infection with highly pathogenic avian influenza A (H5N1) virus reported to WHO, January 2003–March 2009: cluster-associated cases WHO Weekly Epidemiological Record (WER), 15th January 10, 85th YEAR; No. 3, 2010, 85, 13–20 Available from:

The clustering of cases or A(H5N1) outbreaks signifies the possibility of human-to-human transmission of the virus, greater viral transmissibility and potentially the start of an influenza A (H5)-based pandemic. WHO has now published this document following the framework of the IHR regulations which includes individual cases and the clustering of cases or outbreaks of human infection with highly pathogenic avian influenza A (H5N1) over the six year period when the infection has been most active and affected most humans. Clustering has not increased over that period but caution must be expressed because of incomplete surveillance and reporting in some parts of the world.

This study describes the usual experience with the 2009 pandemic influenza in healthy adolescents. It does so by looking at the clinical presentation and course of 2009 pandemic influenza A(H1N1) infection in an outbreak in a  residential summer camp. These camps are a common phenomenon in the USA.  This allowed close investigation and follow-up of a defined but small adolescent population. Through active daily surveillance, medical evaluation at symptom onset and data collection during isolation of subjects the study also had the objective of evaluating the effect of influenza treatment in a summer camp population. The conclusions confirmed how the 2009 pandemic influenza A(H1N1) generally had a mild, self-limited course in healthy adolescent campers and that their recovery normally occured within 72h.

This review describes the characteristics and severity of illness in hospitalized patients in all of New York City over a two week period early in its outbreak of the pandemic virus infection in the summer of 2009 which among other outbreaks led to the declaration of Phase 5 of the pandemic. All the data were collected within 2 weeks and at the time results were made available to the authorities to inform outbreak response measures. The rapid gathering of data contributed to informed recommendations regarding risk and target groups for vaccination in the United States. The review found that the first hospitalized patients in New York City were in younger age groups (91% of these patients were aged <50 years, and 59% were aged <18 years). Only one patient was aged ≥65 years. These findings were consistent with other descriptions of hospitalized persons with H1N1.

The study reports the clinical and epidemiological characteristics of patients hospitalised in the Netherlands for the 2009 pandemic using information from a national mandatory notification system. The notification criteria changed on 15 August 2009 from all possible, probable and confirmed cases to only laboratory-confirmed pandemic influenza hospitalisations and deaths. In the period of comprehensive case-based surveillance (until 15 August), 2% (35/1,622) of the patients with pandemic influenza were hospitalised. From 5 June to 31 December 2009, a total of 2,181 patients were hospitalised. Of these, 10% (219/2,181) were admitted to an intensive care unit (ICU) and 53 died. Among non-ICU hospitalised patients, 56% (961/1,722) had an underlying medical condition compared with 70% (147/211) of the patients in ICU and 46 of the 51 fatal cases for whom this information was reported. Most common complications were dehydration among non-ICU hospitalised patients and acute respiratory distress syndrome among patients in ICU and patients who died. Children under the age of five years had the highest age-specific hospitalisation rate (62.7/100,000), but relatively few were admitted to an ICU (1.7/100,000). The  characteristics and admission rates of hospitalised patients were comparable with reports from other industrialised countries. It is noted that the national notification system was well suited to provide weekly updates of relevant monitoring information on the severity of the pandemic for professionals, decision makers, the media and the public, and could be rapidly adapted to changing information requirements.

From 1 July 2009 to 15 November 2009, 244 patients with 2009 pandemic influenza A(H1N1) were admitted to intensive care unit (ICU) and were compared with 514 cases hospitalised in medical wards in France until 2 November 2009. Detailed case-based epidemiological information and outcomes were gathered for all hospitalised cases. Infants and pregnant women are overrepresented among cases admitted to ICU with 7% for both groups respectively. Overall 20%t of ICU cases did not belong to a risk group. Chronic respiratory disease was the most common risk factor among cases but obesity (body mass index greater or equal to 30 Kg/m2), chronic cardiac disease and immunosuppression were risk factors associated with severe illness after adjustment for age and for other co-morbidities.