Clinical signs in mice vary depending on the strain of virus, strain of mouse and age of mouse. There is lifelong viremia and shedding of virus. Transient runting can occur during the first 3 weeks of life which is sometimes followed by modest growth retardation. At 7-10 months of age, immune complex glomerulonephritis occurs and is characterized by emaciation, rough haircoat, hunched posture, ascites, and possible death. In addition, there is generalized lymphoid hyperplasia and perivascular accumulation of lymphocytes and plasma cells in all visceral organs.
Viremia occurs without any viral shedding.
The outcome is either death within a few days to weeks, or recovery with virus elimination. In experimentally-induced nontolerant infections, the primary pathological lesions are hepatic necrosis, generalized lymphocytolysis of T and B cells, and fibrinoid necrosis of lymphoid organs. Natural infections in hamsters are generally considered subclinical. In humans, the usual clinical manifestations are those of a flu-like illness and include fever, headache, myalgia, nausea, vomiting sore throat, and phobophobia. Occasionally, rash, diarrhea, cough, lymphadenopathy, orchitis, delirium or amnesia occurs.