Investigation of a Pertussis Outbreak in a Daycare Center in Central Taiwan using Pulsed-Field Gel Electrophoresis
2006 Vol.22 NO.2
Pertussis is a respiratory disease transmitted by the inhalation of airborne particles of the saliva or phlegm of an affected person. Before the advent of a Pertussis vaccine, both the incidence and mortality caused by pertussis were high, but the disease is now controlled with vaccine administration. Nowadays, epidemics of pertussis are rare, the majority of cases being sporadic or in family clusters. In April 2005, there was an infant pertussis case which occurred in Taichung. Tracing back contacts in the daycare center and in the family, the grandmother, the director and a nurse of the daycare center were found to be the carriers. In this study, we used pulsed-field gel electrophoresis (PFGE) to analyze strains isolated from the case and the three contacts in order to investigate the epidemiological relationship between them. The four strains were also compared using a DNA map database of Bordetella in order to investigate the dynamic changes among strains. The results of PFGE showed that the four strains had identical PFGE maps, indicating that the case and the contacts were infected from the same source. The results of map comparison showed that the strain was present in the year 2000 in cases from central, northern, and eastern Taiwan, suggesting that the strain may cause endemics around the country. Although it is possible contacts are the infection source of the case, there was no significant elevation of IgA/IgM in contacts, suggesting that contacts were infected for the first time and that it is impossible to differentiate the transmission sequence among contacts and the case. This study shows the importance of case tracing in pertussis infection, especially in daycare centers where infants are in a semi closed group. If workers are carriers, it is very dangerous to the infants.