Volume 18, Number 10—October 2012
Dispatch
Scarlet Fever Epidemic, Hong Kong, 2011
, Janice Y.C. Lo, Amy Z.L. Li, Michael C.K. Lau, Terence K.M. Cheung, Alice Y.M. Wong, Monica M.H. Wong, Christine W. Wong, Shuk-kwan Chuang, and Thomas Tsang
Table 1
Epidemiologic characteristics, clinical features, and laboratory results for scarlet fever cases reported in Hong Kong during January–July 2011 compared with cases reported during 2008–2010
| Characteristic* | 2008–2010, n = 550 | January 1–July 31, 2011, n = 996 | p value |
|---|---|---|---|
| Epidemiology | |||
|
Sex ratio, M:F |
1.6:1 | 1.5:1 | 0.50 |
|
Age range (median) |
9 mo–40 y (5 y) | 1 mo–51 y (6 y) | 0.40 |
|
Local cases |
98.0 (539/550) | 97.4 (970/996) | 0.56 |
| Clustering | |||
|
Cases in a cluster |
5.45 (30/550) | 14.4 (143/996) | <0.0001† |
|
Cases in home clusters |
3.3 (18/550); 9 clusters | 6.5 (65/996); 31 clusters | |
|
Cases in each home cluster, range (median) |
2 (2) | 2–3 (2) | 0.34 |
|
Cases in school clusters |
2.2 (12/550); 4 clusters | 7.8 (78/996); 28 clusters | |
|
Persons affected in each school cluster, no. (median) |
2–4 (3) | 2–7 (2) | 0.42 |
| Clinical features | |||
|
Fever |
95.6 (526/548) | 93.2 (928/996) | 0.065 |
|
Sandpaper rash |
97.4 (534/548) | 95.4 (950/996) | 0.13 |
|
Strawberry tongue |
45.1 (248/550) | 51.4 (512/996) | 0.020‡ |
|
Sore throat |
74.4 (409/550) | 78.5 (782/996) | 0.073 |
|
Desquamation |
27.8 (153/550) | 23.7 (236/996) | 0.084 |
|
Hospitalization |
63.9 (351/549) | 56.6 (561/991) | 0.005§ |
|
Duration of hospitalization, d (mean) |
1– 25 (3.8) | 1–33 (3.3) | 0.005¶ |
|
Concomitant chickenpox |
5.5 (30/550) | 1.9 (19/996) | 0.0002# |
|
Complications** |
0.73 (4/550) | 0.90 (9/996) | 0.79 |
|
Toxic shock syndrome |
0.18 (1/550) | 0.60 (6/996) | 0.43 |
|
Case-fatality rate |
0 | 0.20 (2/996) | 0.54 |
| Laboratory results | |||
|
Laboratory confirmation |
46.0 (253/550) | 51.8 (533/996) | 0.0055†† |
|
Positive throat or wound culture |
95.3 (241/253) | 97.2 (521/533) | 0.094 |
|
Antistreptolysin O titer >200 IU/mL |
4.74 (12/253) | 4.37 (12/533) | 0.094 |
*Values are % (no./total no.) unless otherwise indicated. Lower denominators indicate data missing or not applicable.
†χ2 = 27.
‡χ2 = 5.40.
§χ2 = 7.85.
¶t = –2.8 (95% CI of difference 0.15–0.83 d).
#χ2 = 14.
**Complications include toxic shock syndrome, septicaemia, parapharyngeal abscess, rheumatic fever, quinsy and hepatitis.
††χ2 = 7.7.