Table 2. Possible and Reported Epidemiological Characteristics: Planning Considerations for the Potential pH1N1/09 Fall Wave, from the Public Health Agency of Canada’s Planning Considerations, September 2009.
| World Health Organization’s Areas for Considerationa | Selected Planning Considerations and Estimates from International Sources |
Canadian Areas of Consideration: Selected Planning Considerations, Data and Estimates Relevant to the Canadian Context |
||
|---|---|---|---|---|
|
United States Planning Considerationsb (a plausible scenario for fall resurgence of 2009-H1N1) |
United Kingdom Planning Considerationsc (for the current A(H1N1) influenza pandemic) & U.K. Health Protection Agency Estimates |
Considerations, Data, and Estimates | Source of Information | |
| Total number suspected and confirmed cases | Infection of 30–50% of the U.S. population in the fall and winter (90–150 million infections) Symptoms in 20–40% of the U.S. population (60–120 million) |
4,500 new cases in the UK in the week of 24 August 2009d Weekly number of cases at epidemic peak: 110,000e |
4.5-10.6 million Canadians clinically ill, over possibly three wavesg | Public Health Agency of Canada, Canadian Pandemic Influenza Plan, 2006 |
| British Columbia: project approximately 11,000 courses of antibiotics will be requiredh | Government of British Columbia, British Columbia’s H1N1 Pandemic Influenza Response Plan | |||
| Evidence of concurrent bacterial infection was found in specimens from 22 (29%) of the 77 fatal cases of confirmed 2009 pandemic influenza A (H1N1)i | Northern hemisphere data on pH1N1/09 (Morbidity and Mortality Weekly Report) | |||
| Total number deaths | Estimated deaths: 30,000–90,000 | 70 deaths, cumulative as of 3 September 2009d Estimated number of deaths for the fall wave: 20,000c |
78 deaths, cumulative as of 26 September 2009j | Public Health Agency of Canada, FluWatch data on pH1N1/09 |
| Clinical attack rate | Produce infection of 30–50% of the U.S. population in the fall and winter (90–150 million infections) Symptoms in 20–40% of the U.S. population (60–120 million) |
Up to 30% of populationc Peak clinical attack rate: nationally, up to 6.5% of population per week; locally, 4.5-8.0% of population per weekc |
15-35% over the course of the pandemick | Public Health Agency of Canada, Canadian Pandemic Influenza Plan, 2006 |
| 20-40%l | Other planning considerations on pH1N1/09 (White Paper on Novel H1N1) | |||
| Australia: 20% clinical attack rate; with no intervention, estimated by the end of the winter that 1 in 5 Australians could become infectedm | Southern hemisphere data on pH1N1/09 winter wave | |||
| Case-fatality or mortality rate | - | Estimated case fatality rate reduced from 0.1-0.35% (first major wave)f to 0.1%c | 0.4% in those who are clinically ill (for a pandemic of mild to moderate severity, and in the absence of any interventions, e.g. vaccine, antivirals)k | Public Health Agency of Canada, Canadian Pandemic Influenza Plan, 2006 |
| Comparative health care usage rates between an inter-pandemic and pandemic year: 8.2 times more deaths attributable to influenza during pandemic compared to inter-pandemic yeark | Public Health Agency of Canada, Canadian Pandemic Influenza Plan, 2006 | |||
| Case-fatality or mortality rate | 0.1% case fatality rate for seasonal influenza (4,000 deaths attributed to influenza annually and 10% clinical attack rate), primarily among persons aged 65 years or oldern,o | Canadian data on seasonal influenza | ||
| Highest pH1N1/09 confirmed mortality rate occurred in those over 65 years of age (0.42 per 100,000; spring wave, as of 22 August 2009)p | Public Health Agency of Canada, FluWatch data on pH1N1/09 | |||
| pH1N1/09 confirmed mortality rate 0.23 per 100,000 population in Canada, as of 31 August 2009q | Public Health Agency of Canada data on pH1N1/09 | |||
| Reproduction number (R0) | - | - | 1.4—1.8 (initial wave)k | Public Health Agency of Canada, Canadian Pandemic Influenza Plan, 2006 |
| Other transmission characteristics | Projected peak incidence date (unmitigated): October 15, 2009 At peak incidence, 1–2% of U.S. population infected each day, assuming no change in virus |
Second wave to occur ~ mid-to-late October 2009c | - | - |
a World Health Organization. Considerations for assessing the severity of an influenza pandemic. Weekly epidemiological record (WER). 29 May 2009;84(22):197-202. URL: www.who.int/wer. Date of access: 9 Sept. 2009.
b President’s Council of Advisors on Science and Technology (PCAST). Report to the President on U.S. preparations for 2009-H1N1 influenza. URL: www.whitehouse.gov/assets/documents/PCAST_H1N1_Report.pdf. Date of access: Sept. 2009.
c United Kingdom Department of Health (UKDH). Swine flu: UK planning assumptions (3 September 2009). URL: http://www.businesslink.gov.uk/Horizontal_Services_files/UKplanningassumptions03092009.pdf. Date of access: 3 Sept. 2009.
d Health Protection Agency. Weekly national influenza report. 3 September 2009. URL: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1251473420520.
e Health Protection Agency. Weekly national influenza report. 30 July 2009. URL: http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1248940851283.
f United Kingdom Department of Health (UKDH). Swine flu: UK planning assumptions—SUPERSEDED (16 July 2009). URL: http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_102891.pdf.
g Public Health Agency of Canada. (2006). Canadian Pandemic Influenza Plan for the Health Sector, Annex P. URL: http://www.phac-aspc.gc.ca/cpip-pclcpi/ann-p-eng.php.
h Government of British Columbia. British Columbia’s H1N1 Pandemic Influenza Response Plan (2009): Antibiotics for Secondary Pneumonia in Community and Acute Care Settings. October 2, 2009.
i Bacterial Co-infections in Lung Tissue Specimens from Fatal Cases of 2009 Pandemic Influenza A (H1N1)—United States, May-August 2009. Morbidity and Mortality Weekly Report. October 2, 2009 / 58(38);1071-10.
j Public Health Agency of Canada. FluWatch: September 20, 2009 to September 26, 2009 (Week 38). URL: http://www.phac-aspc.gc.ca/fluwatch/09-10/w38_09/index-eng.php.
k Public Health Agency of Canada. (2006). Canadian Pandemic Influenza Plan for the Health Sector. URL: http://www.phac-aspc.gc.ca/cpip-pclcpi/pdf-e/cpip-eng.pdf.
l Barry, JM. White Paper on Novel H1N1 (Prepared for the MIT Center for Engineering Systems Fundamentals). Massachusetts Institute of Technology Engineering Systems Division, Working Paper Series ESD-WP-2009-07. July 2009. URL: http://esd.mit.edu/WPS/2009/esd-wp-2009-07-072709.pdf.
m Australian Government Department of Health and Ageing. Australian Influenza Surveillance Summary Report No.14, 2009, Reporting period: 8 August 2009—14 August 2009. URL: http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/18D06BAC4644C98DCA25763E00823442/$File/ozflu-no14-2009.pdf.
n Schanzer DL, Langley JM, Tam TWS. Co-morbidities associated with Influenza-Attributed Hospital Admissions and Deaths, 1994-2000, Canada. In: Options for the Control of Influenza VI: June 17-23, 2007, Toronto, Ont., Canada, 2007.
o Schanzer DL, Tam TWS, Langley JM, Winchester BT. Influenza-attributable deaths: Canada 1990-1999. Epidemiol Infect 2007:135;1109-16. (Epub 2007 Feb 19).
p Public Health Agency of Canada. FluWatch: August 23, 2009 to August 29, 2009 (Week 34). URL: http://www.phac-aspc.gc.ca/fluwatch/08-09/w34_09/index-eng.php.
q Public Health Agency of Canada. Deaths associated with H1N1 flu virus in Canada. URL: http://www.phac-aspc.gc.ca/alert-alerte/h1n1/surveillance-archive/20090827-eng.php.