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# 2009 H1N1: Overview of a Pandemic
- URL: https://www.foodconsumer.org/2009_h1n1_overview_of_a_pandemic_0108110805/
- Published: 2011-01-08T09:04:00.000Z
- Updated: 2026-09-22T16:14:32.000Z
- Description: A slide summary of the 2009 H1N1 pandemic: more than 214 countries reported lab-confirmed cases and at least 18,449 deaths, figures the authors call a substantial undercount. Children, young adults, pregnant women and people with chronic conditions were hit hardest.
- Author: Food Consumer
- Tags: Disease, Health News, H1N1, #vivvo-import

# 2009 H1N1: Overview of a Pandemic

Impact of 2009 H1N1

Global Impact

- More than 214 countries and overseas territories or communities had reported laboratory confirmed cases of pandemic influenza H1N1 2009, including at least 18,449 deaths (World Health Organization, August 6, 2010)
- Reported cases and deaths are likely a substantial under-estimate of true impact of 2009 H1N1
- Estimating the true number of individual flu cases and deaths is very challenging
  - Many people with flu don’t seek medical care
  - Only a small number of those that do seek care are tested
  - More people who are hospitalized or die of flu-related causes are tested and reported, but under-reporting of hospitalizations and deaths occurs as well

### Impact of 2009 H1N1 Flu

#### Domestic Impact

  
[http://www.cdc.gov/h1n1flu/estimates\_2009\_h1n1.htm](http://www.cdc.gov/h1n1flu/estimates%5F2009%5Fh1n1.htm?ref=foodconsumer.org)

### Characteristics of 2009 H1N1 Influenza  
April 15, 2009 to April 10, 2010

### Groups at Increased Risk of Severe Influenza (2009 H1N1)

- Most impacted populations
  - Children, young adults
  - Persons with underlying chronic medical conditions (e.g. chronic lung disease, heart disease, immunosuppression, neurological and neurodevelopment diseases)
  - Pregnant women
  - Indigenous populations
- Possible risk groups
  - Obesity (Body Mass Index ≥35), Extreme/Morbid obesity (Body Mass Index ≥40)

### 2009 H1N1 Hospitalizations Frequency of Underlying Conditions in Adults EIP April 15, 2009 – February 16, 2010 (n=4,987)

### Underlying conditions among hospitalized patients and those who died from H1N1 compared to the general population

\*Excludes hypertension

\*\* Morbid obesity is defined as BMI of 40 or higher. For Hospitalized H1N1 patients, BMI calculation was performed on non-pregnant adults ≥ 20 years (n=119). 45% of 119 non-pregnant hospitalized adults ≥ 20 years were missing height and weight information. For Novel H1N1 Deaths, morbid obesity % was calculated for adults only. Prevalence for US non-pregnant adults is based on NHANES (JAMA. 2006;295(13):1577)

Source O Morgan, et al.

### Obesity: a New Risk Factor for Severe Illness due to 2009 H1N1

- Disproportionate number of obese, particularly morbidly obese, among severely ill during 2009 H1N1 pandemic
- Morbid obesity (BMI≥40) was associated with hospitalization, and possibly death, due to 2009 H1N1 infection among adults without chronic medical conditions
- Additional studies with larger sample of patients and appropriate comparison groups are needed

Morgan OW, Bramley A, et al. (2010)

PLoS ONE 5(3): e9694\. doi:10.1371/journal.pone.0009694

### Age-adjusted and Season-specific 2009 H1N1 Influenza-related Hospitalization Rates (per 100,000) by race & ethnicity – Emerging Infections Program, 2009-10

| Race/Ethnicity                                                                 | Influenza Season |      |
| ------------------------------------------------------------------------------ | ---------------- | ---- |
| 2009                                                                           | 2009-10          |      |
| White, non-Hispanic                                                            | 3.0              | 16.3 |
| Black, non-Hispanic                                                            | 10.9             | 29.7 |
| Hispanic                                                                       | 8.2              | 30.7 |
| Asian/Pacific Islander                                                         | 8.1              | 12.5 |
| American Indian/Alaska Native                                                  | 4.1              | 32.7 |
| 2009: April 15 - August 31, 2009 2009-10: September 1, 2009 - January 26, 2010 |                  |      |

### 2009 H1N1 Cumulative Lab-Confirmed Death Rate, by Age Group – April 2009 through March 27, 2010