Ontario Novel H1N1 Influenza A Virus Epidemiologic Summary June 4, 2009 As of 8:30am, June 4, 2009

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1 Ontario Novel H1N1 Influenza A Virus Epidemiologic Summary June 4, 29 As of 8:3am, June 4, 29 Background On April 2, 29, the Public Health Agency of Canada alerted the Ministry of Health and Long-Term Care (MOHLTC) about a number of individuals in various locations in southern and central Mexico with Severe Respiratory Illness (SRI) that were later confirmed as Novel H1N1 Influenza A Virus. On April 28, Ontario received laboratory confirmation of 4 confirmed cases. The epidemiology of cases reported to date in Ontario is summarized below. However, it is expected that the epidemiology of the outbreak in Ontario will change as new cases unrelated to travel to Mexico continue to be identified within the community. The MOHLTC Emergency Operation Centre has been activated and is supported by a scientific response team, with experts drawn from the Ministry, the Ontario Agency for Health Protection and Promotion and the Provincial Infectious Diseases Advisory Committee to provide technical and scientific advice. The Ministry is also providing additional guidance to the public health and healthcare sectors to aid in the early identification and treatment of cases. Ontario is working very closely with the Public Health Agency of Canada, and all provinces and territories. The World Health Organization (WHO) has identified Novel H1N1 Influenza A Virus as a public health emergency of international concern. As of June 4, human cases of swine influenza have been identified in 66 countries around the world. WHO s website provides additional information on the current pandemic level. Up-to-date counts for the Novel H1N1 Influenza A Virus situation can be found at: ONTARIO CANADA USA INTERNATIONAL 1

2 Public Health Surveillance Data of Total Laboratory Confirmed Cases As of 8:3am, June 4, 29 There is a total of 178 laboratory confirmed cases of novel H1N1 Influenza A virus reported in Ontario between April 15 and June 4, 29. Note: Please see Appendix A for the current confirmed provincial surveillance case definition. Table 1. Number of Confirmed Novel H1N1 Influenza A Virus cases in Ontario by health unit, Apr 11 June 4, 29 (N = 178) Health Unit Total Number of Cases Algoma District (2226) Brant County (2227) Chatham-Kent (224) City of Hamilton (2237) 7 City of Ottawa (2251) 51 Durham Region (223) 31 Eastern Ontario (2258) Elgin-St.Thomas (2231) Grey Bruce (2233) 1 Haldimand-Norfolk (2234) Haliburton, Kawartha, Pine Ridge (2235) 1 Halton Region (2236) 88 Hastings & Prince Edward Counties (2238) 2 Huron County (2239) Kingston, Frontenac, Lennox & Addington (2241) 1 Lambton County (2242) Leeds, Grenville and Lanark District (2243)) 1 Middlesex-London (2244) 4 Niagara Region (2246) 1 North Bay Parry Sound District (2247) Northwestern (2249) 1 Oxford County (2252) 1 Peel Region (2253) 186 Perth District (2254) Peterborough County-City (2255) Porcupine (2256) Renfrew County and District (2257) Simcoe Muskoka District (226) 12 Sudbury and District (2261) 3 Thunder Bay District (2262) Timiskaming (2263) 1 Toronto (3895) 51 Waterloo Region (2265) 3 Wellington-Dufferin-Guelph (2266) 7 Windsor-Essex County (2268) 5 York Region (227) 159 Out of Province** 2 Ontario 178 ** Tested in, but not a resident of Ontario 2

3 Case statistics - Novel H1N1 Influenza A Virus Figure 1 shows the age and sex distribution of the 178 confirmed cases. There is no significant difference in the number of reported cases by sex, with 543 cases occurring among males compared to 532 for females. Sex is unknown for 3 cases. In comparison to other age groups, persons under the age of 2 account for over half of all reported confirmed cases. The highest number of confirmed cases of Novel H1N1 Influenza A Virus is among males and females aged Confirmed cases range in age from <1 to 97 years of age; the median age is 16 years and the average age is 22. Initially the majority of confirmed Novel H1N1 Influenza A Virus cases occurred among persons in their twenties; however newer cases are increasingly occurring among younger age groups. The age and sex distribution of cases reported in Ontario may change over time as new cases continue to be identified in the community. Figure 1: Confirmed Novel H1N1 Influenza A Virus cases in Ontario by age group and gender, April 11 to June 4, 29 Number of Confirmed Cases of Novel Influenza A H1N1 Virus FEMALE MALE UNKNOWN < Age Group and Gender UNKNOWN 3

4 Exposure Locations The number of cases acquired in Ontario has been increasing as the virus spreads in the general population, much as seasonal influenza does. The number of Ontario cases of influenza A H1N1 with exposure in Ontario is now greater than the number of cases with exposure to Mexico. Of the 178 laboratory confirmed cases, 54 reported travel to Mexico prior to symptom onset; 579 cases acquired Influenza A H1N1 in Ontario; 12 cases traveled to locations other than Mexico; 99 cases had an unknown exposure and 334 cases did not report an exposure (Table 2a). Table 2a. Exposure among Confirmed Cases in Ontario, Apr 11 June 4, 29 Exposure Confirmed Cases (%) Acquired in Ontario 579 (53.7) Travel to Mexico 54 (5.) Travel to other location 12 (1.1) Unknown 99 (9.2) Did not report 334 (31.) Total 178 (1) Confirmed Cases Acquired in Ontario Among the 579 confirmed cases acquired in Ontario, 373 did not have any known contact with a confirmed case (Table 2b). Through case investigation it was also determined that 196 confirmed cases had contact with known confirmed cases prior to the onset of their illness. The number of cases without any known contact to a confirmed case that had traveled continues to rise. This indicates that broader and sustained community spread is occurring in Ontario. Table 2b. Exposure location for Confirmed Cases acquired in Ontario, Apr 11 June 4, 29 Method of Acquisition in Ontario Number of cases (%) Contact of a traveler to Mexico 8 (1.4) Contact with a confirmed case that traveled to a location other than Mexico 2 (.) Contact with a confirmed case that was acquired in Ontario 196 (33.9) No known contact with a confirmed case 373 (64.4) Total 579 (1) 4

5 Symptoms The most commonly reported symptoms among confirmed cases include cough, fever and sore throat. Symptoms were reported for 774 of 178 laboratory confirmed cases (Table 3). Table 3. Symptoms in Confirmed Cases in Ontario, Apr 11 June 4, 29 Symptoms Number of Confirmed Cases Reporting Symptom COUGH, TOTAL* 715 FEVER, TOTAL* 71 SORE THROAT/HOARSENESS/DIFFICULTY SWALLOWING 332 HEADACHE 254 MYALGIA [MUSCLE PAIN] 252 MALAISE [GENERAL UNWELL FEELING] 213 CHILLS 18 FATIGUE 156 CORYZA [RUNNY NOSE] 145 VOMITING 118 NASAL CONGESTION 115 SHORTNESS OF BREATH 113 DIARRHEA 15 ANOREXIA [LOSS OF APPETITE] 14 SNEEZING 85 NAUSEA 79 ARTHRALGIA [JOINT PAIN] 59 PROSTRATION [EXHAUSTION] 3 DIZZINESS 23 BODY, GENERALIZED ACHES 2 RESPIRATORY DISTRESS 12 CHEST PAIN 11 WEAK 11 EYE, PAIN 7 CHEST CONGESTION 5 PNEUMONIA 5 OTHER** 95 * Fever is the sum of the following symptoms in iphis: (Abnormal Temperature [>= 37.5C OR <=35.5C], Fever, Fever [>=38C OR 1F]) Cough is the sum of the following symptoms in iphis: Cough; Cough, dry; Cough, productive; and Cough, scant ** Other is the sum of all other symptoms reported by all cases 5

6 Current Hospitalizations and Deaths Twenty-nine (2.7% case hospitalization rate)of the confirmed cases have been hospitalized to date. Of these, 23 cases have been discharged. The average length of hospital stay was 5 days, ranging from under 24 hours to 2 days. There are currently 6 confirmed cases that are hospitalized, a number of which have underlying medical conditions. Two deaths have been reported among the confirmed cases (.2% case fatality). Table 4. Current Hospitalizations* among confirmed cases Hospitalization Status Confirmed Number Currently Hospitalized 6 Number Hospitalized and Discharged 23 *Only includes cases admitted to hospital 6

7 Map of confirmed cases The geographic spread of novel H1N1 Influenza A virus is now broader than the Greater Toronto Area (GTA). The highest incidence rates are seen in the GTA. Figure 2. Confirmed cases of novel H1N1 Influenza A virus by Ontario health unit, April 11 June 4, 29 7

8 The epidemic curve of the Novel H1N1 Influenza A Virus outbreak is shown below (Figure 3). Among the confirmed cases, the symptom onset dates range from April 11 to May 3, 29. Additional cases with onset dates after this date are expected to be identified as further laboratory testing and case followup is completed. Figure 3: Confirmed cases of Novel H1N1 Influenza A Virus by Symptom Onset Date in Ontario, Apr 11 June 4, Number of Confirmed Cases of Novel H1N1 Influenza A Virus Apr 13-Apr 15-Apr 17-Apr 19-Apr 21-Apr 23-Apr 25-Apr 27-Apr 29-Apr 1-May 3-May 5-May 7-May 9-May 11-May 13-May 15-May 17-May 19-May 21-May 23-May 25-May 27-May 29-May 31-May 2-Jun 4-Jun Onset Date 8

9 Figure 4: Confirmed cases of Novel H1N1 Influenza A Virus by Symptom Onset Date and Exposure Type in Ontario, Apr 11 June 4, 29* 4 Number of Confirmed Cases of Novel H1N1 Influenza A Virus Apr 13-Apr 15-Apr 17-Apr 19-Apr 21-Apr 23-Apr 25-Apr 27-Apr 29-Apr 1-May 3-May 5-May 7-May 9-May 11-May 13-May 15-May 17-May 19-May 21-May 23-May 25-May 27-May 29-May 31-May 2-Jun 4-Jun Onset Date Acquired in Ontario Travel to Mexico * Does not include confirmed cases that did not acquire illness in Ontario or travel to locations other than Mexico 9

10 Seasonal Influenza Activity As seen in Figure 5, the total number of Influenza A positive cases reported in recent weeks (17-21) is higher than the seasonal peak that was seen in late-february to mid-march (weeks 8-11). The chart below presents cases by week of onset. Figure 5: Confirmed Cases of Influenza A in Ontario by week between September 1 and May 3, * 55 5 Number of Confirmed Cases of Influenza A Week of the Year SOURCE: Ontario Ministry of Health and Long-Term Care, integrated Public Health Information System (iphis) database, extracted [4/6/29]. Episode Date for a case corresponds to the earliest date on record for the case according to the iphis hierarchy (Symptom Date > Clinical Diagnosis Date > Specimen Collection Date > Lab Test Date > Reported Date) * For Week 2, decreased influenza case counts may be attributed in part to reporting delays Detailed summaries of seasonal influenza activity and the Ontario Influenza Bulletin are available on the Ministry of Health and Long-term Care s website at: 1

11 Ontario Agency for Health Protection and Promotion Laboratory Surveillance Report Information current as of: Wednesday June 3, 29 at 1am The number of patient specimens tested at the Central Public Health Lab (CPHL) is displayed in this section. Information in this report is current as of Wednesday June 3, 29 at 1am; updated information becomes available every Wednesday at 1am. The CPHL performs the majority of testing for this outbreak; however, several hospital labs also perform novel H1N1 influenza A testing. When novel H1N1 influenza A is detected in specimens at the hospital labs, the specimen is sent to CPHL for confirmation. Numbers reported here may not reconcile precisely with those reported through the integrated Public Health Information System (iphis) as hospital lab results may be reported in iphis before they are entered and confirmed at CPHL. Testing Procedure for Novel H1N1 Influenza A Virus The Central Public Health Lab (CPHL) is testing patient specimens for the novel H1N1 influenza A virus which is a subtype of the influenza A virus; therefore specimens are first tested for influenza A and if the virus is detected the specimen is then sub-typed for the novel H1N1 influenza A virus as well as seasonal influenza A subtypes H1 and H3. As of June 2, 29, a total of 9386 patients have been tested at the Central Public Health Lab (CPHL) for novel H1N1 Influenza A virus. A summary of test results by specimen collection week can be found in Table 5. Of the 9386 patients tested, 992 (1.6%) tests detected novel H1N1 Influenza A virus and 765 (81%) did not detect the virus. There are 789 (8.4%) patient test results pending which include 299 suspect cases that have detected influenza A, but are still awaiting subtyping information. The number of novel H1N1 influenza A cases detected each week appears to be increasing over time, with 39.3% (n=39) of all novel H1N1 cases detected in the most recent week (May 24-3, 29). In contrast, the number of Influenza A (Other/ Human) cases detected has decreased over time with only 1.3% (n=53) of all Influenza A (Other/ Human) cases detected during the week of May 24-3, 29, compared to 34.2% of all cases detected 3 weeks prior (April 26- May 2, 29). The increase in novel H1N1 influenza A cases may be due in part to wider spread within communities. Table 5. Patient test results for specimens collected between April 1- June 2, 29, tested at the Central Public Health Lab, Ontario. Specimen collection date 1 Number of Number of Number of Number of Positive Positive Negative Positive for Total Influenza A, Influenza A Cases (for novel H1N1 Cases Pending (Other/ novel H1N1 Influenza A Tested novel H1N1 Human) Influenza A virus Cases (Suspect) virus) Week 13 (March 29- April 4) 5 5 Week 14 (April 5-11) Week 15 (April 12-18) Week 16 (April Week 17 (April 26- May 2) Week 18 (May 3-9) Week 19 (May 1-16) Week 2 (May 17-23) Week 21 (May 24-3) May 31- June Total Source: Central Public Health Laboratories, Ontario Agency for Health Protection and Promotion (OAHPP). 11

12 (1)Note: For 1268 specimens, no collection date was yet available; the date the specimen was received at the lab has been used as a proxy. The frequency of patients tested for the novel H1N1 influenza A virus at CPHL by result and specimen collection date is presented in Figure 6. The right side of the graph appears to demonstrate a steep decrease in testing recently; however dates after May 29, 29 should be interpreted with caution due to lab reporting lag times, testing delays and the high number of pending tests. Figure 6. Number of patients tested for novel H1N1 Influenza A virus in Ontario and result of test by specimen collection date, April 1-June 2, Number of Patients Tested /4/9 3/4/9 5/4/9 7/4/9 9/4/9 11/4/9 13/4/9 15/4/9 17/4/9 19/4/9 21/4/9 23/4/9 25/4/9 27/4/9 29/4/9 Specimen Collection Date 1/5/9 3/5/9 5/5/9 7/5/9 9/5/9 11/5/9 13/5/9 15/5/9 17/5/9 19/5/9 21/5/9 23/5/9 25/5/9 27/5/9 29/5/9 31/5/9 2/6/9 Detected (novel H1N1 influenza A) Not Detected (novel H1N1 influenza A) Pending Source: Central Public Health Laboratories, Ontario Agency for Health Protection and Promotion (OAHPP). (1) Note: For 1268 specimens, no collection date was available; the date the specimen was received at the lab has been used as a proxy. Over half (55.2%) of all patients tested were female; of the lab confirmed cases, 49.1% are female (data not shown). The age distribution by result of patient specimens tested for novel H1N1 Influenza A virus is shown in Figure 7; the patients who have pending results are not included in this graph (N=784). Over one-third (34.2%) of all patient specimens being tested are submitted from children under the age of 19. Patient specimens submitted by adults between the ages of 2 and 49 make up 4.4% of all tests. School age children (aged 5-19) comprise 23% of all testing; however, these same children make up 42.2% of all positive influenza A (other/ human and novel H1N1) cases. This may be due to several school clusters that have recently been reported. 12

13 Figure 7. Age distribution by result of patient specimens tested for novel H1N1 Influenza A virus, specimen collection dates April 1- June 2, 29 (1) Number of Patients Tested Unknown Age Novel H1N1 Detected Influenza A (Other/ Human) Influenza A Not detected Source: Central Public Health Laboratories, Ontario Agency for Health Protection and Promotion (OAHPP). (1) Note: Age was not available for 61 patients. The age distribution of novel H1N1 influenza A positive cases and median age by specimen collection week is displayed in Figure 8. Over half of all novel H1N1 influenza A cases are between the ages of - 19; the 1-19 age group is growing rapidly across the weeks. This has resulted in the median age of cases dropping over time which is likely due to school clusters that have been reported in several areas. The median age is the age that separates the higher half of a group from the lower half. 13

14 Figure 8. Age distribution of novel H1N1 influenza A cases and median age, by specimen collection week, April 19- May 3, Number of novel H1N1 influenza A cases Age Week 16 Week 17 Week 18 Week 19 Week 2 Week 21 Specimen Collection Week Median Age Source: Central Public Health Laboratories, Ontario Agency for Health Protection and Promotion (OAHPP). 14

15 Appendix A Current Provincial Surveillance Case Definition (as of May 5, 29): Confirmed Person with Influenza-like illness 1 and Laboratory confirmation of swine influenza A (H1N1) virus infection by one or more of the following tests: RT-PCR with genotyping of H1 and/or N1 swine influenza virus Viral culture with strain typing Four-fold rise in swine influenza A(H1N1) virus specific antibodies by serology testing 1 Influenza-like illness: Acute onset of respiratory illness with fever AND one or more of the following - cough, sore throat, arthralgia, myalgia, prostration, or malaise. In cases under 5 or 65 and older fever may not be prominent. 15