In some patients the illness can progress to a severe form with haemorrhagic manifestations and hepatitis; possible complications include retinitis (inflammation of the retina) and encephalitis (inflammation of the brain).
Pri nekaterih bolnikih se lahko razvijejo hude oblike s hemoragičnimi manifestacijami in hepatitisom; možni zapleti pa vključujejo tudi retinitis (vnetje očesne mrežnice) in encefalitis (vnetje možganov).