 In a fatal attack , however , it manifests very quickly . In a number of cases , death has occurred within 24 hours of the onset of the infection , while other cases do not last longer than around five days . The virus attacks endothelial cells , rupturing capillaries and causing blood loss and haemorrhaging ; once this reaches the heart , the haemorrhage kills quickly through shock . Symptoms include lethargy and an unwillingness to eat , a rapid heartbeat , and decreased blood @-@ cell count , as well as cyanosis of the tongue , mouth ulcers , and oedema of the head and trunk . 
