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Volume 22, Number 1—January 2016

Avian Influenza A(H7N9) Virus Infection in 2 Travelers Returning from China to Canada, January 20151

Danuta SkowronskiComments to Author , Catharine Chambers, Reka Gustafson, Dale B. Purych, Patrick Tang, Nathalie Bastien, Mel Krajden, and Yan Li
Author affiliations: British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada (D.M. Skowronski, C. Chambers, P. Tang, M. Krajden); University of British Columbia, Vancouver (D.M. Skowronski, R. Gustafson, D.B. Purych, P. Tang, M. Krajden); Vancouver Coastal Health Authority, Vancouver (R. Gustafson); LifeLabs Medical Laboratories, Surrey, British Columbia, Canada (D.B. Purych); Public Health Agency of Canada, Winnipeg, Manitoba, Canada (N. Bastien, Y. Li); University of Manitoba, Winnipeg (Y. Li)

Main Article

Table 2

Antibody titers to influenza A/Anhui/1/2013(H7N9) in an anonymized population serosurvey, Lower Mainland, British Columbia, Canada, May 2013*

Age group, y No. patients† Median age, y % Female Mean GMT (95% CI)‡ No. (%, 95% CI)§
With titer >10 With titer >20
<10 49 4 47 5 0 0
10–19 48 16 67 5 0 0
20–29 49 27 69 5 0 0
30–39 50 34 90 5 0 0
40–49 50 46 60 5 0 0
50–59 49 55 49 5 0 0
60–69 50 65.5 56 5.3 (4.9–5.7) 3 (6.0, 0.0–12.6) 1 (2.0, 0–5.9)¶
70–79 50 75 42 5 0 0
80–89 50 83 40 5.4 (5–5.9) 4 (8.0, 0.5–15.5) 1 (2.0, 0–5.9)¶
5.3 (4.9–5.6)
3 (5.9, 0.0–12.4)
1 (2.0, 0–5.8)¶
All 496 50 59 5.1 (5–5.2) 10 (0.9, 0.2–1.7)# 3 (0.3, −0.1 to 0.7)#

*Titers were measured by hemagglutination inhibition assay by using horse erythrocytes as previously described (6); assays were conducted at the National Microbiology Laboratory, Canada’s influenza reference laboratory in July 2013. GMT, geometric mean titer.
†Serum samples were collected in May 2013; 5 samples had insufficient serum and were excluded from the analyses (8).
‡Titers were assessed in duplicate. Titers <10 were assigned a value of 5. GMT of duplicate titers derived as individual titers and group GMTs derived by age and overall.
§No patients had a titer >40.
¶Further assessed by microneutralization (MN) assay, according to procedures described by the Centers for Disease Control and Prevention (Atlanta, GA, USA); available by request. MN titers for all 3 samples were <10.
#Age-standardized (direct method) to the 2013 Fraser Valley and Greater Vancouver, British Columbia, Canada, population projections (BC Stats, 2013:

Main Article

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Main Article

1Preliminary results from the population serosurvey were presented at the CACMID-AMMI Canada 2014 Annual Conference, April 3–5, 2014, Victoria, British Columbia, Canada.

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