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Original Articles
Alarm Thresholds for Pertussis Outbreaks in Iran: National Data Analysis
Yousef Alimohamadi, Seyed Mohsen Zahraei, Manoochehr Karami, Mehdi Yaseri, Mojtaba Lotfizad, Kourosh Holakouie-Naieni
Osong Public Health Res Perspect. 2020;11(5):309-318.   Published online October 22, 2020
DOI: https://doi.org/10.24171/j.phrp.2020.11.5.07
  • 2,746 View
  • 40 Download
  • 1 Citations
AbstractAbstract PDF
Objectives

The purpose of the current study was to determine the upper threshold number of cases for which pertussis infection would reach an outbreak level nationally in Iran.

Methods

Data on suspected cases of pertussis from the 25th February 2012 to the 23rd March 2018 from the Center for Disease Control and Prevention in Iran was used. The national upper threshold level was estimated using the exponentially weighted moving average (EWMA) method and the Poisson regression method.

Results

In total, 2,577 (33.6%) and 1,714 (22.3%) cases were reported in the Spring and Summer respectively. There were 1,417 (18.5%) and 1,971 (25.6%) cases reported in the Autumn and Winter, respectively. The overall upper threshold using the EWMA and the Poisson regression methods, was estimated as a daily occurrence of 8 (7.55) and 7.50 (4.48–11.06) suspected cases per 10,000,000 people, respectively. The daily seasonal thresholds estimated by the EWMA and the Poisson regression methods were 10, 7, 6, 8 cases and 10, 7, 7, 9 cases for the Spring, Summer, Autumn, and Winter, respectively.

Conclusion

The overall and seasonal estimated thresholds by the 2 methods were similar. Therefore, the estimated thresholds of 6–10 cases in a day, per 10,000,000 people could be used to detect pertussis outbreaks and epidemics by health policymakers.

Comparing Seasonal Pattern of Laboratory Confirmed Cases of Pertussis with Clinically Suspected Cases
Golam Reza Ghorbani, Seyed Mohsen Zahraei, Mahmood Moosazadeh, Mahdi Afshari, Fahimeh Doosti
Osong Public Health Res Perspect. 2016;7(2):131-137.   Published online April 30, 2016
DOI: https://doi.org/10.1016/j.phrp.2016.02.004
  • 1,419 View
  • 18 Download
  • 10 Citations
AbstractAbstract PDF
Objectives
During recent decades, there has been limited attention on the seasonal pattern of pertussis within a high vaccine coverage population. This study aimed to compare the seasonal patterns of clinical suspected pertussis cases with those of laboratory confirmed cases in Iran.
Methods
The current study was conducted using time series methods. Time variables included months and seasons during 2011–2013. The effects of seasons and months on the incidence of pertussis were estimated using analysis of variance or Kruskal–Wallis.
Results
The maximum average incidence of clinically confirmed pertussis was 23.3 in July (p = 0.04), but the maximum incidence of clinical suspected pertussis was 115.7 in May (p = 0.6). The maximum seasonal incidences of confirmed and clinical pertussis cases were reported in summer (average: 12, p = 0.004), and winter (average: 108.1; p = 0.4), respectively.
Conclusion
The present study showed that the seasonal pattern of laboratory confirmed pertussis cases is highly definite and different from the pattern of clinical suspected cases.
Multilocus Sequence Analysis of Housekeeping Genes and Antigenic Determinant Genes in Bordetella pertussis Strains Isolated in Korea
Sang-Oun Jung, Yu Mi Moon, So-Hyeon Kim, Hwa Young Sung, Seung-Jik Kwon, Yeon Ho Kang, Jae Yon Yu
Osong Public Health Res Perspect. 2011;2(2):115-126.   Published online June 30, 2011
DOI: https://doi.org/10.1016/j.phrp.2011.08.003
  • 1,465 View
  • 13 Download
  • 2 Citations
AbstractAbstract PDF
Objectives
To confirm genotype diversities of clinical isolates of Bordetella pertussis and to evaluate the risk of pertussis outbreak in Korea.
Methods
Seven housekeeping genes and 10 antigenic determinant genes from clinical B. pertussis isolates were analyzed by Multilocus sequence typing (MLST).
Results
More variant pattern was observed in antigenic determinant genes. Especially, PtxS1 gene was the most variant gene; five genotypes were observed from eight global genotypes. In the bacterial type, the number of observed sequence types in the isolates was seven and the most frequent form was type 1 (79.6%). This major sequence type also showed a time-dependent transition pattern. Older isolates (1968 and 1975) showed type 1 and 6 in housekeeping genes and antigenic determinant genes, respectively. However, these were changed to type 2 and 1 in isolates 1999–2008. This transition was mainly attributed to genotype change of PtxS1 and Fim3 gene; the tendency of genotype change was to avoid vaccine-derived genotype. In addition, there was second transition in 2009. In this period, only the sequence type of antigenic determinant genes was changed to type 2. Based Upon Related Sequence Types (BURST) analysis confirmed that there were two clonal complexes (ACCI and ACCII) in the Korean isolates. Moreover, the recently increased sequence type was revealed as AST2 derived from AST 3 in ACCI.
Conclusions
Genotype changes in Korean distributing strains are still progressing and there was a specific driving force in antigenic determinant genes. Therefore continuous surveillance of genotype change of the distributing strains should be performed to confirm interrelationship of genotype change with vaccine immunity.

PHRP : Osong Public Health and Research Perspectives