TABLE 3.
Acute respiratory illness (ARI), a influenza illness and influenza hospitalization during the epidemic periods b by the trimester of symptom onset in the annual cohorts of China respiratory illness surveillance among pregnant women (CRISP), Suzhou, 2015/2016–2017/2018 seasons
| ARI incidence (per 100 person‐months, 95% CI) | p | Influenza incidence (per 100 person‐months, 95% CI) | p | Influenza hospitalization, n/N (% of influenza ARI) | p | |
|---|---|---|---|---|---|---|
| Overall | 13/411 (3.2) | |||||
| First | 21.0 (19.5, 22.6) | REF | 1.4 (1.0, 1.9) | REF | 0/39 (0.0) | REF |
| Second | 10.0 (9.5, 10.5) | <0.001 | 1.2 (1.0, 1.4) | 0.419 | 1/151 (0.7) | |
| Third | 7.6 (7.2, 7.9) | <0.001 | 1.2 (1.0, 1.3) | 0.333 | 12/221 (5.4) | 0.005 |
| 2015/2016 | 3/66 (4.5) | |||||
| First | 17.6 (15.3, 20.0) | REF | 0.7 (0.2, 1.3) | REF | 0/6 (0.0) | REF |
| Second | 8.3 (7.4, 9.4) | <0.001 | 0.7 (0.4, 1.0) | 1.000 | 0/22 (0.0) | |
| Third | 6.3 (5.7, 6.9) | <0.001 | 0.7 (0.5, 0.9) | 0.941 | 3/38 (7.9) | 0.256 |
| 2016/2017 | 8/158 (5.1) | |||||
| First | 22.8 (20.6, 24.9) | REF | 1.2 (0.6, 1.8) | REF | 0/17 (0.0) | REF |
| Second | 11.2 (10.3, 11.8) | <0.001 | 1.0 (0.7, 1.2) | 0.527 | 0/59 (0.0) | |
| Third | 8.4 (7.8, 9.0) | <0.001 | 1.0 (0.8, 1.3) | 0.728 | 8/82 (9.8) | 0.007 |
| 2017/2018 | 3/187 (1.6) | |||||
| First | 22.6 (18.6, 26.7) | REF | 3.8 (2.1, 5.6) | REF | 0/16 (0.0) | REF |
| Second | 9.5 (8.5, 10.5) | <0.001 | 2.1 (1.7, 2.6) | 0.063 | 1/70 (1.4) | |
| Third | 7.7 (7.0, 8.4) | <0.001 | 2.0 (1.6, 2.4) | 0.032 | 2/101 (2.0) | 1.000 |
Abbreviations: CI, confidence interval; REF, reference.
Acute respiratory illness (ARI) defined as ≥1 respiratory symptom (cough, sore throat, stuffy nose, chest pain, and difficulty breathing) and ≥1 systemic symptom (feverish, temperature ≥38°C, chills, headache) or ≥2 respiratory symptoms with onset within the last 10 days.
The start of each influenza epidemic period was defined as the first day of three consecutive influenza reporting weeks in which the percentage of specimens testing positive for any influenza virus infection was higher than 5%. The end of each influenza epidemic period was defined as the day before the first of three consecutive influenza reporting weeks in which the percentage of specimens testing positive for influenza was below 5%.