The mortality from plague may be about 90 per cent. or more when the epidemic is at its height. In the beginning, or towards the end of the epidemic, the mortality is less, as it is the case with all other epidemic diseases. The average mortality at Bombay has been 84 per cent. and in Karachi 89 per cent. It is, therefore, more fatal than all other epidemic diseases, the mortality from cholera during the height of an epidemic being about 60 per cent.

In children and in the aged the disease is more fatal than in healthy adults. Cases in which the bubo appears early and is single, or in which there is a distinct morning remission, or less general prostration or free perspiration, or in which there is no diarrhoea, have greater chance of recovery. Rapid suppuration of the buboes indicates a favourable termination. Buboes do not suppurate as a rule until the primary fever has fallen. On the other hand, carbuncles, multiple buboes (specially on the neck), meningitis, hÆmorrhages, pleurisy, pneumonia, diarrhoea, gastric irritation, cyanosis, jaundice and continued pyrexia are unfavourable signs.