Studies of immune responses in MERS-CoV patients in Saudi Arabia and South Korea demonstrate that high viral loads, lymphopenia, and thrombocytopenia as well as high neutralizing antibody titers and higher numbers of virus-specific CD4 T cells were associated with increased disease severity and death implicating a role for both humoral and cell-mediated immunity in MERS-CoV disease (59, 60). Here, CD4 is linked to lymphopenia.