ELISA analyses of serum samples from the three patients from whom the CS5+CS6 positive strains E1777, E1779, and E1785 had been isolated showed that on day 7 (early convalescence) the patients infected with E1777 and E1785 had developed strong IgG as well as IgA immune responses against CS5, whereas the patient infected with strain E1779, who had a co-infection with V. cholerae Ogawa, had developed only a very modest immune response (IgA and IgG) against CS5 (Fig. 1). The gene discussed is CSHL1; the disease is coinfection.