Cytotoxic CD4+ T are consistently identified in a number of chronic viremic states, including mice infected with lymphocytic choriomeningitis virus and gamma-herpes virus, and patients with human immunodeficiency virus, cytomegalovirus, Epstein-Barr Virus, and hepatitis B and C (Jellison et al., 2005; Soghoian et al., 2012; van Leeuwen et al., 2004; Sáez-Borderías et al., 2006; Suni et al., 2001, Aslan et al., 2006); however, these cells are also generated in acute viremias such as influenza (Brown et al., 2012). Here, CD4 is linked to influenza.