IFNA1 and infection: However, if innate antiviral immune system deficiencies allow low viral burdens to overcome host antiviral defenses—for example, in individuals with deficiencies in innate immune signals or those with autoantibodies against type I IFNs—or if infections involve high viral loads, as seen in this study where a lethal dose (1×105 pfu) was administered intranasally to mice, the IFN response becomes insufficient to control initial viral replication.