Another question on susceptibility is regarding whether 2019-nCoV infection confers neutralising immunity, usually but not always, indicated by the presence of neutralising antibodies in convalescent sera. Some experts already questioned whether the 2019-nCoV may behave similarly to MERS-CoV in cases exhibiting mild symptoms without eliciting neutralising antibodies [17]. A separate question pertains to the possibility of antibody-dependent enhancement of infection or of disease [18,19]. If either of these were to be relevant, the transmission dynamics could become more complex.