Arrange the sentences A, B, C and D in a proper sequence so as to make a coherent paragraph.

A. It begins with an ordinary fever and a moderate cough.

B. India could be under attack from a class of germs that cause what are called atypical pneumonias.

C. Slowly, a sore throat progresses to bronchitis and then pneumonia and respiratory complications.

D. It appears like the ordinary flu, but baffled doctors find that the usual drugs don't work.