en Infectious Diseases Research (Original) <strong>Background:</strong> Nematodes of <em>Trichostrongylus</em> genus are mainly parasites of herbivores, although human infections in sporadic form &lrm; have been reported worldwide&lrm;<span dir="RTL">.</span> Herein we reported an outbreak of trichostrongyliasis in Qaemshar city in Mazandaran province, north of Iran from May to June 2020.&nbsp;<br> <strong>Methods:</strong> The investigation was designed as a retrospective cross-sectional study on an outbreak occurred in Qaemshahr city in the north of Iran. The diagnosis of trichostrongyliasis cases was confirmed by hypereosinophilia and existence of <em>Trichostrongylus</em> &lrm; eggs in the stool.<br> <strong>Results: </strong>Trichostrongyliasis &lrm; diagnosed in twelve patients. The age range of patients was &lrm;10-78 years old. 83.5% of the patients were female and &lrm;75% of them lived in the rural area. &nbsp;&lrm; The most common &lrm;<span dir="RTL">&rlm; &rlm;</span>signs and symptoms of patients were abdominal pain&lrm; 91.6%, diarrhea 83.3%, &lrm;vomiting 41.6%, nausea 50%, anemia &lrm;&lrm;&lrm;&lrm;8.3% and chill &lrm; &lrm;16.6% respectively. &lrm; These patients undertook a course of treatment consisting of antihelminth &lrm;drug &lrm;for adult &lrm;and albendazole for children.&lrm; Symptoms of trichostrongyliasis &lrm; improved completely after therapy&lrm;<span dir="RTL">.</span><br> <strong>Conclusions: </strong>Our study indicated that trichostrongyliasis may be a major parasitic aetiology for gastrointestinal symptoms such as abdominal pain among rural residents in endemic areas with outbreak presentations. Trichostronyliasis, Outbreak, rural area 0 0 http://tbsrj.mazums.ac.ir/browse.php?a_code=A-10-1964-1&slc_lang=en&sid=1 Farhang Babamahmoodi farhang.baba@yahoo.com 100319475328460029478 100319475328460029478 No Antimicrobial Resistance Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Fatemeh Ahangarkani fkani63@gmail.com 100319475328460029479 100319475328460029479 No Antimicrobial Resistance Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Fatemeh Bahrami Dounchali bahramifateme.med@gmail.com 100319475328460029480 100319475328460029480 No Student research committee, Antimicrobial Resistance Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Atabak Nikbakht nikbakht.atabak@gmail.com 100319475328460029481 100319475328460029481 Yes Student research committee, Faculty of medicine, Isfahan University of Medical Sciences, Isfahan, Iran