Abstract Introduction Hajj pilgrimage is the biggest and longest mass gathering in the Muslim world. Annually, about 50% of more than 2.5 million pilgrims participating in this ritual get involved in severe devastating coughs. Most coughs continue, so the pilgrims turn back home and transmit them to family members and other people. Despite the high prevalence of coughs for many years, what causes them remains unknown. Considering the pertussis-like clinical picture of the so-called “hajj coughs”, the researchers conducted a study to measure antibodies against three known common atypical bacteria, namely Bordetella Pertussis, Chlamydia Pneumonia and Mycoplasma Pneumonia. Patients and methods The study was done on three out of eleven groups of pilgrims from Yazd province, central Iran. The sample was selected randomly and consisted of 202 pilgrims who completed an informed consent. Their blood samples were taken, and the plasma was separated and then stored at -70 °C. After turning back from the journey, the pilgrims had their second blood samples taken. As many as 52 pilgrims failed to come for the second sampling, and two samples were broken during transportation. The final analysis was performed on the remaining 148 pairs of samples. Results Antibodies were already elevated in many pilgrims before the journey probably due to their old age (causing more exposure to pathogens) or unplanned pertussis vaccination. After their return, antibody elevation was only mild, again probably due to the old age of the participants (i.e. due to their weaker immune systems). Some antibodies even fell down without any known reason. In this study, previous hajj journey was assumed as a prophylactic factor, due to acquisition of immunity. Coughs with a prolonged pertussis-like picture were also presumed to be more related than other types of coughs to atypical pathogens. Statistical tests showed that the history of previous journeys had no prophylactic effect. Also, no correlation was found between the clinical pictures of coughs and infection with atypical bacteria. Conclusion Even though some rises and falls occurred in the antibodies titer, the variations could hardly be attributed to coughs in this study. Indeed, the variation of antibodies had no meaningful relationship with clinical factors. In this regard, further studies are needed to clarify the reason for the so-called “hajj coughs”, but epidemiological studies will be difficult to do until easier and more reliable methods become available for accurate diagnosis.
Hajj . Cough . Mass gathering . Seroepidemiology . Respiratory tract infections . Bordetella Pertussis . Mycoplasma Pneumonia . Chlamydia Pneumonia.