Field and epidemiological investigations during the 2009 influenza pandemic conducted in the United States: similar approaches in diverse settingsArchived

2009 H1N1 Influenza Pandemic: Field and Epidemiological Investigations in the United States at the Start of the First Pandemic of the 21st Century Swerdlow DL, Finelli L and Bridges CBOxford Journals – Clinical Infectious Diseases; Volume 52 suppl. 1

1 January 2011

This paper serves as a gateway review of several field and epidemiological investigations conducted across the United States (US) which have been compiled as a special supplement in a January 2011 number of the Clinical Infectious Diseases journal. These investigations were critical, the authors argue, in helping answering many questions that arose in the initial phase, i.e. severity, transmissibility of the virus, sustainability of the transmission, geographical spread, its relation with underlying conditions and so on. In addition, these studies also contributed to characterise at the beginning of the pandemic the virus and the pandemic itself. From April 2009, many epidemiological questions such as length of viral shedding, the ability to efficient spread among people and the severity features required rapid evaluation to inform decision makers in the countries affected about the use of mitigation strategies and countermeasures, both pharmaceutical and non-pharmaceutical. In view of the authors, these investigations and surveillance reports paint a picture of a rapidly spreading virus with the greatest impact in children and young adults, limited impact relative to seasonal influenza and past pandemics among older adults, and identification of some previously unrecognised and/or rediscovered high-risk groups, like morbidly obese people and native Alaskan/American populations. 

Overall, the supplement includes a total of 29 reports of surveillance, field studies and epidemiologic investigations, as follows:

2009 H1N1 Influenza Pandemic: Field and Epidemiologic Investigations in the United States at the Start of the First Pandemic of the 21st Century Swerdlow DL, Finelli L and Bridges CBClin Infect Dis. (2011) 52(suppl 1): S1-S3

Perspective: Swine-Origin Influenza: 1976 and 2009 Sencer DJClin Infect Dis. (2011) 52(suppl 1): S4-S7

The Science behind Preparing and Responding to Pandemic Influenza: The Lessons and Limits of Science Schuchat A, Bell BP and Redd SCClin Infect Dis. (2011) 52(suppl 1): S8-S12

Epidemiology of 2009 Pandemic Influenza A (H1N1) in the United States Jhung MA, Swerdlow D, Olsen SJ, et al.Clin Infect Dis. (2011) 52(suppl 1): S13-S26

Surveillance for Influenza during the 2009 Influenza A (H1N1) Pandemic–United States, April 2009–March 2010 Brammer L, Blanton L, Epperson S, et al.Clin Infect Dis. (2011) 52(suppl 1): S27-S35

Detecting 2009 Pandemic Influenza A (H1N1) Virus Infection: Availability of Diagnostic Testing Led to Rapid Pandemic Response Jernigan DB, Lindstrom SL, Johnson JR, et al.Clin Infect Dis. (2011) 52(suppl 1): S36-S43

Influenza Pandemic Epidemiologic and Virologic Diversity: Reminding Ourselves of the Possibilities Kasowski EJ, Garten RJ and Bridges CB Clin Infect Dis. (2011) 52(suppl 1): S44-S49

Hospitalized Patients with 2009 Pandemic Influenza A (H1N1) Virus Infection in the United States—September–October 2009 Skarbinski J, Jain S, Bramley A, et al.Clin Infect Dis. (2011) 52(suppl 1): S50-S59

Epidemiology of 2009 Pandemic Influenza A (H1N1) Deaths in the United States, April–July 2009 Fowlkes AL, Arguin P, Biggerstaff MS, et al.Clin Infect Dis. (2011) 52(suppl 1): S60-S68

2009 Pandemic Influenza A (H1N1) Deaths among Children—United States, 2009–2010 Cox CM, Blanton L, Dhara R, et al.Clin Infect Dis. (2011) 52(suppl 1): S69-S74

Estimating the Burden of 2009 Pandemic Influenza A (H1N1) in the United States (April 2009–April 2010) Shrestha SS, Swerdlow DL, Borse RH, et al.Clin Infect Dis. (2011) 52(suppl 1): S75-S82

Timely Assessment of the Severity of the 2009 H1N1 Influenza Pandemic Armstrong GL, Brammer L and Finelli L Clin Infect Dis. (2011) 52(suppl 1): S83-S89

Influenza-Like Illness in the Community during the Emergence of 2009 Pandemic Influenza A(H1N1) – Survey of 10 States, April 2009 Reed C, Angulo FJ, Biggerstaff M, et al.Clin Infect Dis. (2011) 52(suppl 1): S90-S93

Influenza-Like Illness in a Community Surrounding a School-Based Outbreak of 2009 Pandemic Influenza A (H1N1) Virus–Chicago, Illinois, 2009 Janusz KB, Cortes JE, Serdarevic F, et al.Clin Infect Dis. (2011) 52(suppl 1): S94-S101

Viral Shedding Duration of Pandemic Influenza A H1N1 Virus during an Elementary School Outbreak—Pennsylvania, May–June 2009 Bhattarai A, Villanueva J, Palekar RS, et al.Clin Infect Dis. (2011) 52(suppl 1): S102-S108

Virus Detection and Duration of Illness Among Patients With 2009 Pandemic Influenza A (H1N1) Virus Infection in Texas Suryaprasad A, Morgan OW, Peebles P, et al.Clin Infect Dis. (2011) 52(suppl 1): S109-S115

Diagnosis of 2009 Pandemic Influenza A (pH1N1) and Seasonal Influenza Using Rapid Influenza Antigen Tests, San Antonio, Texas, April–June 2009 Donnelly CA, Finelli L, Cauchemez S, et al.Clin Infect Dis. (2011) 52(suppl 1): S116-S122

Serial Intervals and the Temporal Distribution of Secondary Infections within Households of 2009 Pandemic Influenza A (H1N1): Implications for Influenza Control Recommendations Donnelly CA, Finelli L, Cauchemez S, et al.Clin Infect Dis. (2011) 52(suppl 1): S123-S130

Transmission of 2009 Pandemic Influenza A (H1N1) at a Public University—Delaware, April–May 2009 Guh A, Reed C, Gould LH, et al.Clin Infect Dis. (2011) 52(suppl 1): S131-S137

Non-Pharmaceutical Interventions during an Outbreak of 2009 Pandemic Influenza A (H1N1) Virus Infection at a Large Public University, April–May 2009 Mitchell T, Dee DL, Phares CR, et al.Clin Infect Dis. (2011) 52(suppl 1): S138-S145

Household Transmission of 2009 Pandemic Influenza A (H1N1) and Nonpharmaceutical Interventions among Households of High School Students in San Antonio, Texas Loustalot F, Silk BJ, Gaither A, et al.Clin Infect Dis. (2011) 52(suppl 1): S146-S153

An Outbreak of 2009 Pandemic Influenza A (H1N1) Virus Infection in an Elementary School in Pennsylvania Marchbanks TL, Bhattarai A, Fagan RP, et al.Clin Infect Dis. (2011) 52(suppl 1): S154-S160

Investigating 2009 Pandemic Influenza A (H1N1) in US Schools: What Have We Learned Iuliano AD, Dawood FS, Silk BJ, et al.Clin Infect Dis. (2011) 52(suppl 1): S161-S167

Closing Schools in Response to the 2009 Pandemic Influenza A H1N1 Virus in New York City: Economic Impact on Households Borse RH, Behravesh CB, Dumanovsky T, et al.Clin Infect Dis. (2011) 52(suppl 1): S168-S172

A Model Survey for Assessing 2009 Pandemic Influenza A (H1N1) Virus Disease Burden in the Workplace Gindler J, Grohskopf LA, Biggerstaff M, et al.Clin Infect Dis. (2011) 52(suppl 1): S173-S176

A Survey of Emergency Department 2009 Pandemic Influenza A (H1N1) Surge Preparedness—Atlanta, Georgia, July–October 2009 Sugerman D, Nadeau KH, Lafond K, et al.Clin Infect Dis. (2011) 52(suppl 1): S177-S182

HIV-Infected Hospitalized Patients with 2009 Pandemic Influenza A (pH1N1)—United States, Spring and Summer 2009 Peters PJ, Skarbinski J, Louie JK, et al.Clin Infect Dis. (2011) 52(suppl 1): S183-S188

2009 Pandemic Influenza A H1N1 in Alaska: Temporal and Geographic Characteristics of Spread and Increased Risk of Hospitalization among Alaska Native and Asian/Pacific Islander People Wenger JD, Castrodale LJ, Bruden DL, et al.Clin Infect Dis. (2011) 52(suppl 1): S189-S197

Transmission of Pandemic (H1N1) 2009 Influenza to Healthcare Personnel in the United States Wise ME, De Perio M, Halpin J, et al.Clin Infect Dis. (2011) 52(suppl 1): S198-S204

ECDC Comment (17 March 2011):

Influenza surveillance systems aim at rapidly detecting the start of yearly winter epidemics, monitor their geographical spread, characterise the circulating viruses and determine their severity in terms of mortality and hospitalisations rates. Epidemiological information such as transmission dynamics, risk factors for severity, clinical attack rates, pathogenicity, etc are not usually investigated during seasonal influenza epidemics [1].  As compared to other diseases such as food and water born infections for which there are consolidated outbreak investigation practices and protocols, Influenza outbreaks are seldom thoroughly investigated.

As a new influenza virus emerged and spread worldwide in 2009, it was therefore challenging to rapidly gather essential information to implement the appropriate prevention and mitigation strategies through field investigations. This Supplement issue of the Clinical Infectious Disease Journal present wide range of field epidemiological studies and surveillance systems that were implemented in the United States to shed light on the main epidemiological and virological pandemic influenza Unknowns. On some occasions investigations were complex to implement and results were probably not timely enough to guide interventions. However a great amount of experience was gathered in terms of appropriate study designs and surveillance methods which will prove useful to rapidly and efficiently deal with future influenza threats.

These investigations proved extremely useful also for European countries that were affected by the pandemic later than the United States. In particular they allowed European countries to adapt their interventions and pandemic plans accordingly thus avoiding the implementation of more disruptive measures that were planned for the worst case scenario of an A(H5N1) influenza pandemic.

Protocols and surveillance systems developed and/or strengthened during the 2009 pandemic are important undertakings, however the current challenge is to maintain them operational during inter-pandemic years and ready to be used when the next pandemic starts.