The Experience of the Retrospective Epidemiological Analysis of Outbreaks of Pertussis in the Moscow Suburbs

Background Pertussis outbreaks are continuously observed in different countries despite many years of specific prophylaxis measures for this infection, use of whole-cell and acellular vaccines and use of different schemes of immunization. In our country, even with the overall morbidity stabilization, outbreaks of pertussis continue to be recorded even in regions where the situation was satisfactory previously. As a rule, the majority of epidemic pertussis foci were limited to 1 case of disease (without spread of infection) -86.4% in average. The prevalence of mild clinical forms of disease that are hard to detect, poor effectiveness of the bacteriological method used for examination of exposed persons, and a decrease in the number of examined persons suggest underreporting of whooping cough cases. The most reliable information on the epidemic process manifestations of pertussis can be obtained during outbreaks. Therefore, we conducted a review of outbreaks of pertussis in a small town of district subordinance. Materials and methods As methods of our study we used retrospective epidemiological analysis, serological and molecular genetic methods. The main sources of information were emergency reports and epidemiological investigation of pertussis. Results and discussion From July 28, 2015 to March 24, 2016 year 58 cases of pertussis were observed. Three secondary schools, two grammar schools, five kindergartens, one trade school and the children not attending any educational facility were affected by the outbreak of whooping cough. In the end, during the outbreak, there were 6 foci in kindergartens, 1 focus in the trade school, 18 -in secondary schools, 53 household foci, with the number of patients ranging from 1 to 18. Age distribution was as follows: 50 children (86.2%), 6 adolescents (10.3%) and 2 (3.5%) adults. Among those, 9 people have not been vaccinated against pertussis, with three more also considered un-vaccinated due to an unknown vaccination status, and three children received just one dose of the DPT vaccine; 43 patients had been vaccinated against pertussis, including one who received three doses of the vaccine, 41 had a booster pertussis vaccination. In most cases the source of infection could not be established. 44 patients had a mild form of whooping cough, while 1 case was a combination of pertussis and parapertussis, and 13 patients had medium or severe form of the disease. Conclusion The almost simultaneous identification of whooping cough cases by a number of institutions suggest the existence hidden pertussis cases. Despite the fact that vaccination in household foci is not indicted, it is still possible to prevent the spread of pertussis. It was enough to suspect whooping cough in children coughing for more than 7 days and order laboratory examination to avoid any prolonged stay of an infection source in an organized collective. Overcrowded accommodation in neighbourhoods, close contacts of children at neighborhood playgrounds in neighborhoods and supplementary education classes were the factors that allowed the infection to spread to many institutions of the city