en Infectious Diseases Infectious Diseases Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="color:#0000ff;"><strong><em>Background</em></strong><em>:</em></span> A few studies compared the epidemiologic features of the first and second waves of coronavirus disease 2019 (COVID-19) outbreak. This research was carried out to compare the 1^st and the 2^nd waves of the epidemics in the northern Iran.<br> <span style="color:#0000ff;"><strong><em>Methods</em></strong><em>:</em></span> In this observational research, demographic, clinical and laboratory characteristics of the patients with COVID-19, admitted to four government hospitals affiliated to Babol University of Medical Sciences during the 1^st and the 2^nd waves of COVID-19 epidemics have been compared. The period from May 21, 2020 to September 21, 2020 was considered as the second wave of the epidemics while from February 19, 2020 to May 20, 2020, as the first wave of the outbreak in this region<span dir="RTL">.</span><br> <span style="color:#0000ff;"><strong><em>Results</em></strong><em>:</em></span> Out of 6691 total hospitalized cases, 4374 (65.37%), including 1532 (49.6%) people in the first wave and 2842 (78.9%) in the second wave had RT-PCR test for disease confirmation. Among those who were examined with RT-PCR test, 2322 patients (53.1%) including 728 (31.4%) persons in the first wave and 1594 (68.6%) in the second wave were positive for SARS-CoV-2 RNA. 414 (56.9%) of the confirmed cases in the first wave and 767 (48.1%) in the second wave were males (p<0.001). Gastrointestinal symptoms were more incidental in the second wave of the disease. However, severe respiratory conditions were more common during the first wave (p<0.001). Crude mortality rate was lower in the second wave of the outbreak (p<0.001).<br> <span style="color:#0000ff;"><strong><em>Conclusion</em></strong><em>:</em></span> Different epidemiologic characteristics were found in the second wave of COVID-19 outbreak in comparison with the first wave of the epidemics in northerrn Iran.</span></span> Coronavirus, Epidemiology, Disease outbreaks, IRAN, Babol 544 550 http://caspjim.com/browse.php?a_code=A-10-95-5&slc_lang=en&sid=1 Seyed Farzad Jalali alibijani@yahoo.com 100319475328460026459 100319475328460026459 No Department of Cardiology, Babol University of Medical Sciences, Babol, Iran Mostafa Ghassemzadeh alibijani@yahoo.com 100319475328460026460 100319475328460026460 No Department of Dermatology, Babol University of Medical Sciences, Babol, Iran Simin Mouodi alibijani@yahoo.com 100319475328460026461 100319475328460026461 No Social Determinants of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Mostafa Javanian alibijani@yahoo.com 100319475328460026462 100319475328460026462 No Infectious Diseases and Tropical Medicine Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Mehdi Akbari Kani alibijani@yahoo.com 100319475328460026463 100319475328460026463 No Babol University of Medical Sciences, Babol, Iran Reza Ghadimi alibijani@yahoo.com 100319475328460026464 100319475328460026464 No Social Determinants of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Ali Bijani alibijani@yahoo.com 100319475328460026465 100319475328460026465 Yes Social Determinants of Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran