Background
Methods
Data sources
Emergency Department data
Laboratory data
Data analysis
Poisson regression models
Cross-correlation analysis
Qualitative comparison of medium to long term trends
Comparison of smoothed raw time series
Estimate of laboratory processing and reporting delays
Results
Descriptive statistics
ED provisional diagnosis of influenza | Laboratory-notified influenza infection | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Influenza season (May-Sep) | Rest of year |
Total
| Influenza season (May-Sep) | Rest of year |
Total
| ||||||||
No. | % | No. | % |
No.
|
%
| No. | % | No. | % |
No.
|
%
| ||
Age group
| 0–4 yrs | 1108 | 14% | 567 | 14% |
1675
|
14%
| 1298 | 40% | 90 | 7% |
1388
|
31%
|
5–9 yrs | 526 | 7% | 162 | 4% |
688
|
6%
| 210 | 6% | 33 | 3% |
243
|
5%
| |
10–14 yrs | 487 | 6% | 166 | 4% |
653
|
5%
| 162 | 5% | 41 | 3% |
203
|
4%
| |
15–19 yrs | 825 | 11% | 437 | 10% |
1262
|
11%
| 118 | 4% | 60 | 5% |
178
|
4%
| |
20–24 yrs | 930 | 12% | 553 | 13% |
1483
|
12%
| 102 | 3% | 105 | 8% |
207
|
5%
| |
25–29 yrs | 710 | 9% | 489 | 12% |
1199
|
10%
| 108 | 3% | 97 | 8% |
205
|
5%
| |
30–34 yrs | 705 | 9% | 400 | 10% |
1105
|
9%
| 128 | 4% | 108 | 8% |
236
|
5%
| |
35–39 yrs | 558 | 7% | 302 | 7% |
860
|
7%
| 118 | 4% | 93 | 7% |
211
|
5%
| |
40–44 yrs | 435 | 6% | 281 | 7% |
716
|
6%
| 116 | 4% | 79 | 6% |
195
|
4%
| |
45–49 yrs | 374 | 5% | 182 | 4% |
556
|
5%
| 98 | 3% | 71 | 6% |
169
|
4%
| |
50–54 yrs | 283 | 4% | 159 | 4% |
442
|
4%
| 94 | 3% | 78 | 6% |
172
|
4%
| |
55–59 yrs | 215 | 3% | 111 | 3% |
326
|
3%
| 98 | 3% | 79 | 6% |
177
|
4%
| |
60–64 yrs | 143 | 2% | 95 | 2% |
238
|
2%
| 118 | 4% | 73 | 6% |
191
|
4%
| |
65–69 yrs | 122 | 2% | 74 | 2% |
196
|
2%
| 112 | 3% | 74 | 6% |
186
|
4%
| |
70–74 yrs | 126 | 2% | 79 | 2% |
205
|
2%
| 101 | 3% | 70 | 5% |
171
|
4%
| |
75–79 yrs | 93 | 1% | 41 | 1% |
134
|
1%
| 94 | 3% | 57 | 4% |
151
|
3%
| |
80–84 yrs | 84 | 1% | 34 | 1% |
118
|
1%
| 99 | 3% | 34 | 3% |
133
|
3%
| |
85+ yrs | 76 | 1% | 34 | 1% |
110
|
1%
| 101 | 3% | 32 | 3% |
133
|
3%
| |
Unknown | 0 | 0% | 1 | 0% |
1
|
0%
| 0 | 0% | 1 | 0% |
1
|
0%
| |
Sex
| Male | 3767 | 48% | 2063 | 50% |
5830
|
49%
| 1671 | 51% | 569 | 45% |
2240
|
49%
|
Female | 4032 | 52% | 2104 | 50% |
6136
|
51%
| 1601 | 49% | 705 | 55% |
2306
|
51%
| |
Admission status
| Admitted | 434 | 6% | 193 | 5% |
627
|
5%
| N/A | N/A | N/A | N/A | N/A | N/A |
Not Admitted | 7360 | 94% | 3966 | 95% |
11326
|
95%
| N/A | N/A | N/A | N/A | N/A | N/A | |
Influenza type
| A | N/A | N/A | N/A | N/A | N/A | N/A | 2635 | 80% | 974 | 76% |
3609
|
79%
|
B | N/A | N/A | N/A | N/A | N/A | N/A | 534 | 16% | 235 | 18% |
769
|
17%
| |
Both A & B | N/A | N/A | N/A | N/A | N/A | N/A | 43 | 1% | 47 | 4% |
90
|
2%
| |
Unspecified | N/A | N/A | N/A | N/A | N/A | N/A | 63 | 2% | 19 | 1% |
82
|
2%
| |
Area of residence
| Major cities | 4094 | 52% | 2209 | 53% |
6303
|
53%
| 2495 | 76% | 985 | 77% |
3480
|
76%
|
Inner regional | 2452 | 31% | 1261 | 30% |
3713
|
31%
| 517 | 16% | 184 | 14% |
701
|
15%
| |
Outer regional | 990 | 13% | 546 | 13% |
1536
|
13%
| 216 | 7% | 83 | 7% |
299
|
7%
| |
Remote | 205 | 3% | 81 | 2% |
286
|
2%
| 24 | 1% | 5 | 0% |
29
|
1%
| |
Total
|
7800
|
100%
|
4167
|
100%
|
11967
|
100%
|
3275
|
100%
|
1275
|
100%
|
4550
|
100%
|
Poisson regression models
Ljung-Box Test | |||
---|---|---|---|
Year | Time series | Q-statistic | P-value |
2001 | ED | 11.72 | 0.07 |
Laboratory model | 8.29 | 0.22 | |
2002 | ED | 14.60 | 0.02* |
Laboratory | 5.26 | 0.51 | |
2003 | ED | 4.36 | 0.63 |
Laboratory | 6.16 | 0.41 | |
2004 | ED | 3.25 | 0.78 |
Laboratory | 4.25 | 0.64 | |
2005 | ED | 3.25 | 0.78 |
Laboratory | 13.71 | 0.03* | |
2001 to 2005 | ED | 11.72 | 0.16 |
Laboratory | 13.58 | 0.09 |
Cross-correlation analysis
Year | The highest and statistically significant correlation coefficient | P value | Lag of highest correlation (days) |
---|---|---|---|
2001 | 0.12 | 0.02 | -11 |
2002 | 0.14 | 0.01 | -18 |
2003 | 0.12 | 0.03 | -4 |
2004 | 0.12 | 0.03 | -3 |
2005 | 0.11 | 0.02 | -4 |
2001 to 2005 | 0.06 | 0.01 | -3 |