This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'During a cholera epidemic, what is the first step to be taken? \nSelect and explain. \nA. Safe water supply and sanitation, B. Cholera vaccination to all individuals, C. Primary chemoprophylaxis, D. Treat everyone with tetracycline', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pattenkoffer advocated "improving local sanitary conditions as \'the best way to prevent or stop cholera Epidemics" Robe Koch believed that quarantine and disinfection can only prevent cholera Cholera Cholera is an acute diarrhoea disease caused by Vibrio cholera Vibrio cholera : \'Gram-negative bacterium\' that produces cholera toxin (enterotoxin), which act on C-AMP system of mucosal cells of epithelium lining of the small intestine (to cause massive diarrhoea) Classic biotype El Tor biotype (serotypes: Ogawa , Inaba and Hikojima) Incubation period : 1-2 days (Few hours - 5 days) Reservoir : Human beings only Rice-water diarrhoea Essentials for treatment of cholera : Water and electrolyte replacement (ORS) Ref: Park 25th edition Pgno : 247-256', 'role': 'assistant'}]