Infant Pertussis and Household Transmission in Korea

Kwon, Hyo Jin; Yum, Sook Kyung; Choi, Ui Yoon; Lee, Soo Young; Kim, Jong Hyun; Kang, Jin Han

The highest numbers of pertussis cases was in April, June, and September, which have relatively warm temperatures in Korea. Few patients occurred in winter as other respiratory pathogens are commonly considered in the differential diagnosis. Similar studies from other countries have also shown that the reported pertussis case mostly occurred in a summer months with high temperatures (21, 22) . Since the number of patients is too small, it is unclear to know the seasonality of pertussis based only upon this result. In addition, various factors such as environmental factors, school opening, and climate can affect the seasonal characteristics of pertussis epidemiology. However, because clinical presentations of pertussis often resemble influenza-like symptoms and those of other respiratory diseases such as Mycoplasma pneumoniae and adenovirus, this lack of awareness and nonspecific clinical characteristics may be often associated with underdiagnosed condition of pertussis. The diagnostic tool of pertussis is challenging. Culture of nasopharyngeal secretions is essential for diagnosis, however, the result showed the lowest sensitivity (42.9%) in our patients. Moreover, this result requires a long incubation period up to 10 to 14 days, after which the patient can be delayed in critical treatment and infect other persons with contact. The majority of confirmed cases were based in the presence of PCR. Although RT-PCR and serological test were not performed in all patients, these methods also have higher sensitivity than culture. Serologic testing can help the diagnosis of patients with atypical symptoms, for whom clinical samples are collected at later time from the onset of disease.