Severity of swine flu in the United States

December 07, 2009

Research published this week in PLoS Medicine presents the most accurate assessment to date of the severity of the swine flu (H1N1) pandemic in the US.

Scientists need to measure the severity of swine flu (how often infection with the swine flu virus results in symptoms leading to illness, hospitalization or death) so that appropriate pandemic plans can be put into place. Severity of swine flu has been difficult to measure for two main reasons: first, people with severe influenza are more likely than those with mild cases to seek care, making it difficult to estimate how many total cases have occurred, and second, the sheer number of cases means that recording routine case data can be difficult due to overburdening of public health systems.

In this study, Anne Presanis, Marc Lipsitch and colleagues combined two large datasets, (gathered between April and July, 2009) from Milwaukee (where all medically attended cases were recorded, whether hospitalized or not) and New York City (where only hospitalizations, intensive care admission and deaths were recorded, and a telephone survey of flu-like illness was conducted), along with earlier results from studies by the US CDC, using a statistical approach called Bayesian evidence synthesis. This enabled accurate estimations of severity to be made.

Their analyses reveal that the autumn-winter pandemic wave of swine flu should have a death toll only slightly higher than, or considerably lower than, that caused by seasonal influenza in an average year, provided swine flu continues to behave as it did during the summer. Seasonal influenza mainly kills elderly adults, but the authors reveal that most deaths from swine flu will occur in non-elderly adults, a shift in age distribution that has been seen in previous pandemics.

A preliminary version of this article was posted on PLoS Currents Influenza (on September 25th 2009) to aid dissemination of this important information during the pandemic.
Citation: Presanis AM, De Angelis D, The New York City Swine Flu Investigation Team, Hagy A, Reed C, et al. (2009) The Severity of Pandemic H1N1 Influenza in the United States, from April to July 2009: A Bayesian Analysis. PLoS Med 6(12): e1000207. doi:10.1371/journal.pmed.1000207

Funding: AMP and DDA were funded by the UK Medical Research Council grants G0600675 and U.1052.00.007. DDA was funded also by the UK Health Protection Agency. ML and SR were supported by Cooperative Agreements 1U54GM088558 and 5U01GM076497 of the Models of Infectious Disease Agent Study program of the US National Institutes of Health (US NIH). SR also received funding from grant 3R01TW008246-01S1 from the US NIH from the RAPIDD program of the Fogarty International Center of the US NIH and the Science and Technology Directorate of the US Department of Homeland Security. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: ML has received consulting fees from the Avian/Pandemic Flu Registry (Outcome Sciences), sponsored in part by Roche




Marc Lipsitch
Harvard School of Public Health
Epidemiology and Immunology and Infectious Diseases
Harvard School of Public Health
677 Huntington Avenue
Boston, MA 02115
United States of America
+1 617 432 4559
+1 617 566 7805 (fax)

About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit


Related Pandemic Articles from Brightsurf:

Areas where the next pandemic could emerge are revealed
An international team of human- and animal health experts has incorporated environmental, social and economic considerations -- including air transit centrality - to identify key areas at risk of leading to the next pandemic.

Narcissists love being pandemic 'essential workers'
There's one group of essential workers who especially enjoy being called a ''hero'' during the COVID-19 pandemic: narcissists.

COVID-19: Air quality influences the pandemic
An interdisciplinary team from the University of Geneva and the ETH Z├╝rich spin-off Meteodat investigated possible interactions between acutely elevated levels of fine particulate matter and the virulence of the coronavirus disease.

People who purchased firearms during pandemic more likely to be suicidal
People who purchase a firearm during the pandemic are more likely to be suicidal than other firearm owners, according to a Rutgers study.

Measles outbreaks likely in wake of COVID-19 pandemic
Major measles outbreaks will likely occur during 2021 as an unexpected consequence of the COVID-19 pandemic, according to a new academic article.

The COVID-19 pandemic: How US universities responded
A new George Mason University study found that the majority of university announcements occurred on the same day as the World Health Organization's pandemic declaration.

Researchers find evidence of pandemic fatigue
A new study from the USC Leonard Davis School of Gerontology shows that the behavioral responses to COVID-19 differed by age.

Excessive alcohol consumption during the COVID-19 pandemic
The full impact of COVID-19 on alcohol use is not yet known, but rates have been rising during the first few months of the pandemic.

How fear encourages physical distancing during pandemic
Despite guidelines plastered on the walls and floors of grocery and retail stores encouraging customers to maintain six-feet of physical distance during the pandemic, many do not.

COVID-19 pandemic and $16 trillion virus
This Viewpoint aggregates mortality, morbidity, mental health conditions, and direct economic losses to estimate the total cost of the pandemic in the US on the optimistic assumption that it will be substantially contained by the fall of 2021.

Read More: Pandemic News and Pandemic Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to