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Scarlet fever outbreak, Hong Kong, 2011.
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PMID:  23017843     Owner:  NLM     Status:  MEDLINE    
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Authors:
Eric H Y Lau; Hiroshi Nishiura; Benjamin J Cowling; Dennis K M Ip; Joseph T Wu
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Type:  Letter; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Emerging infectious diseases     Volume:  18     ISSN:  1080-6059     ISO Abbreviation:  Emerging Infect. Dis.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-09-28     Completed Date:  2013-02-19     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  9508155     Medline TA:  Emerg Infect Dis     Country:  United States    
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Languages:  eng     Pagination:  1700-2     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Child
Child, Preschool
China / epidemiology
Disease Outbreaks*
Hong Kong / epidemiology
Humans
Macau / epidemiology
Scarlet Fever / epidemiology*,  microbiology*
Streptococcus pyogenes / isolation & purification*
Grant Support
ID/Acronym/Agency:
U54 GM088558/GM/NIGMS NIH HHS; U54 GM088558/GM/NIGMS NIH HHS
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Journal Information
Journal ID (nlm-ta): Emerg Infect Dis
Journal ID (iso-abbrev): Emerging Infect. Dis
Journal ID (publisher-id): EID
ISSN: 1080-6040
ISSN: 1080-6059
Publisher: Centers for Disease Control and Prevention
Article Information
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Print publication date: Month: 10 Year: 2012
Volume: 18 Issue: 10
First Page: 1700 Last Page: 1702
PubMed Id: 23017843
ID: 3471616
Publisher Id: 12-0062
DOI: 10.3201/eid1810.120062

Scarlet Fever Outbreak, Hong Kong, 2011 Alternate Title:Scarlet Fever, Hong Kong
Eric H.Y. Lau
Hiroshi Nishiura
Benjamin J. Cowling
Dennis K.M. Ip
Joseph T. Wu
The University of Hong Kong School of Public Health, Hong Kong Special Administrative Region, People’s Republic of China (E.H.Y. Lau, H. Nishiura, B.J. Cowling, D.K.M. Ip, J.T. Wu);
and Japan Science and Technology Agency, Saitama, Japan (H. Nishiura)
Correspondence: Address for correspondence: Eric H.Y. Lau, School of Public Health, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, People’s Republic of China; email: ehylau@hku.hk

To the Editor: Scarlet fever is a notifiable disease in Hong Kong, Guangdong Province, and Macau in the People’s Republic of China. All 3 areas reported substantial increases in cases during 2011 (Figure, panel A). In Hong Kong, individual data, including age, geographic location, date of notification, and travel history within the incubation period, were collected from all locally notified scarlet fever case-patients. As of December 31, 2011, a total of 1,535 cases (21.7 cases/100,000 population) were reported, which was ≈10× higher than the average number of annual cases reported during the preceding 10 years (1). Of those, 730 cases were laboratory confirmed; 46 cases were imported; and 2 cases, 1 each in a 7-year-old girl and a 5-year-old boy co-infected with chickenpox, resulted in death (2).

Group A Streptococcus (GAS), the bacterium that causes scarlet fever, is mainly transmitted by direct contact with saliva and nasal fluids from infected persons (3). Many children can also carry GAS or be asymptomatically infected (4). A recent study in China showed that GAS is commonly resistant to macrolides and tetracycline but sensitive to penicillin, chloramphenicol, cefradine, and ofloxacin (5). In Hong Kong, GAS emm type 12 dominated among the isolates cultured during 2011 (6). Most of the cases reported were in children <10 years of age (range 1 month–51 years; median 6 years [interquartile range 4–7 years]). The age distribution is similar to that reported during previous years (data not shown).

In the United Kingdom during the mid-19th century, scarlet fever epidemics were found to follow a 5- to 6-year cycle, but this pattern disappeared as incidence decreased (7). Annual scarlet fever notifications in Hong Kong remained low during 2001–2010 (<4 cases/100,000 population) and did not demonstrate any apparent long-term pattern. The recent increase in scarlet fever notifications might be attributable to antigenic drift, increase in virulence of GAS (8), or increased circulation of GAS. However, other than mandatory notification of medically attended case-patients, systematic laboratory testing of GAS isolates was not conducted in Hong Kong, and these possibilities could not be further investigated.

Notifications of scarlet fever usually peak during December–March in Hong Kong, but the outbreak in 2011 peaked in June (Figure, panel B). The rise in scarlet fever cases in Guangdong Province and Macau slightly preceded that in Hong Kong; cases in Guangdong peaked in April (Figure, panel A). Maximum cross-correlations between spline-interpolated weekly scarlet fever notifications in Guangdong and Macau and those in Hong Kong were found at 1- and 2-week lags, respectively (ρ = 0.45 and 0.58) (Technical Appendix).

In 2011, scarlet fever notification rates were elevated in all 4 regions of Hong Kong: New Territories East, New Territories West, Kowloon, and Hong Kong Island at 27.2, 21.7, 18.9, and 19.6 cases per 100,000 population, respectively. However, a distinctly higher proportion of imported cases before July 2011 (12 of 14, p value for exact binomial test = 0.01) were notified in New Territories East and New Territories West, where the main border crossings to mainland China are located. This finding suggests a link to the outbreak in Guangdong in these regions during the early phase of the local outbreak.

We estimated the instantaneous reproduction number (Rt), which measures the time-dependent frequency of transmission per single primary case (Technical Appendix) (9). An Rt consistently >1 would indicate sustained local transmission. We estimated Rt on the basis of the daily scarlet fever notification data in different periods, adjusted for imported cases. For 19 cases (1.2% of all cases), we could not determine whether infection was local or imported. We estimated Rt in 2 different ways: either by assuming that all of these cases were local or by assuming that they all were imported, to represent possible extreme values of Rt. Rt fluctuated between 0.6 and 2.0 and was consistently >1 from mid-May through the end of June. Rt fell quickly to <1 beginning in early July after 2 fatal scarlet fever cases were reported on May 29 and June 21, which raised widespread concern in the community (Figure, panel C). Heightened surveillance, publicity, health education to the public (Technical Appendix) were implemented by the Centre for Health Protection in early June and could have contributed to the reduction in transmissibility. The health education measures included guidance on prevention and control measures, such as updates of antimicrobial drug resistance profile of GAS issued to all doctors and strengthening reporting of scarlet fever cases by child care centers and schools for prompt epidemiologic investigations.

In summary, we analyzed the notification data of scarlet fever and investigated spatiotemporal spreading patterns of the disease with certain time lags in Hong Kong, Macau, and Guangdong. The estimated Rt in 2011 indicated the potential for local transmission and persistence. Such a borderless spread indicates a critical need to enhance cross-border communication and timely sharing of epidemic information so that future disease control efforts can be made at multiple geographic levels.

Technical Appendix

Statistical methods and discussion of impact of public notification of disease transmission, scarlet fever outbreak, Hong Kong, 2011.



Notes

Suggested citation for this article: Lau EHY, Nishiura H, Cowling BJ, Ip DKM, Wu JT. Scarlet fever outbreak, Hong Kong, 2011 [letter]. Emerg Infect Dis [Internet]. 2012 Oct [date cited]. http://dx.doi.org/10.3201/eid1810.120062

Acknowledgments

We thank S.K. Chuang and Thomas Tsang of the Centre for Health Protection in Hong Kong for their kind support and assistance in collating the notification data. We thank Peng Wu for technical support.

This project was supported by the Harvard Center for Communicable Disease Dynamics from the National Institute of General Medical Sciences (grant no. U54 GM088558) and the Research Fund for the Control of Infectious Diseases, Food and Health Bureau, Government of the Hong Kong Special Administrative Region (grant no. HKU-11-04-02). H.N. received funding support from JST PRESTO program. B.J.C. received research funding from MedImmune Inc.. D.K.M.I. received research funding from F. Hoffmann-La Roche Ltd.


References
1. . Centre for Health Protection, Government of the Hong Kong Special Administrative Region Number of notifications for notifiable infectious diseases, Year: 2011 [cited 2012 Jan 11]. http://www.chp.gov.hk/en/notifiable1/10/26/43.html
2. . Centre for Health Protection, Government of the Hong Kong Special Administrative Region Update on scarlet fever in Hong Kong [cited 2012 Jun 30]. http://www.chp.gov.hk/files/pdf/ltd_20110622_scarlet_fever_update.pdf
3. . Centers for Disease Control and Prevention Scarlet fever: a group A streptococcal infection. Year: 2011 [cited 2011 Sep 1]. http://www.cdc.gov/Features/ScarletFever
4. . ShaikhN, LeonardE, MartinJMPrevalence of streptococcal pharyngitis and streptococcal carriage in children: a meta-analysis.Pediatrics. Year: 2010;126:e557–6410.1542/peds.2009-264820696723
5. . LiangY, ShenX, HuangG, WangC, ShenY, YangYCharacteristics of Streptococcus pyogenes strains isolated from Chinese children with scarlet fever.Acta Paediatr. Year: 2008;97:1681–510.1111/j.1651-2227.2008.00983.x18691162
6. . LauMCK Increase in scarlet fever cases in 2011. Communicable Diseases Watch. Year: 2011; 8:48–9 [cited 2012 Jun 30]. http://www.chp.gov.hk/files/pdf/cdw_v8_12.pdf
7. . DuncanCJ, DuncanSR, ScottSThe dynamics of scarlet fever epidemics in England and Wales in the 19th century.Epidemiol Infect. Year: 1996;117:493–910.1017/S09502688000591618972674
8. . KöhlerW, GerlachD, KnöllHStreptococcal outbreaks and erythrogenic toxin type A.Zentralbl Bakteriol Mikrobiol Hyg [A]. Year: 1987;266:104–15 .10.1016/S0176-6724(87)80024-x3122461
9. . NishiuraH, ChowellG The effective reproduction number as a prelude to statistical estimation of time-dependent epidemic trends. In: Chowell G, Hayman JM, Bettencourt LMA, editors. Mathematical and statistical estimation approaches in epidemiology. New York: Springer; Year: 2009 p. 103–21.

Figures

[Figure ID: F1]
Figure 

Trends in scarlet fever during outbreak in Hong Kong, Guangdong, and Macau, People’s Republic of China, 2011. A) Monthly scarlet fever notifications in Hong Kong, Guangdong (data obtained from Department of Health Guangdong Province, www.gdwst.gov.cn/a/yiqingxx), and Macau (data obtained from Health Bureau, Government of the Macau Special Administrative Region (www.ssm.gov.mo/news/content/ch/1005/statistic.aspx). Vertical tick marks indicate January of each year. Data from Guangdong and Macau were available beginning in 2005. Black line indicates data from Hong Kong; gray line, data from Guangdong; broken line, data from Macau; gray bar, number of imported cases in Hong Kong, 2005-2011. B) Weekly notifications of scarlet fever cases in Hong Kong and monthly notifications in Guangdong and Macau. Black line indicates data from Hong Kong; gray line, data from Guangdong; broken line, data from Macau. C) Estimated instantaneous reproduction number (Rt) and 95% pointwise confidence intervals (CIs) based on scarlet fever notifications in Hong Kong, February–December, 2011. Black line indicates estimate calculated by grouping patients with unknown importation status with patients with imported cases; gray line, estimate calculated by grouping patients with unknown importation status with local case-patients; broken lines, the upper and lower limits of the 95% CIs for Rt. For better presentation, CIs are shown only for the former estimates. Horizontal line indicates the critical value of Rt, under which transmission of disease will not be sustainable.



Article Categories:
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Article Categories:
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Keywords: Keywords: scarlet fever, group A streptococcus, bacteria, Hong Kong, China, outbreak.

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