All are true for Point source epidemic except
EPIDEMIC:
• Definitions of epidemic:
– Occurrence of no. of cases of a disease ‘clearly in excess of normal expectancy (NE)’
1. Normal expectancy is derived by looking at average of no. of cases of the disease in previous 3 – 5 years in that geographical area
2. If NE = zero, ‘even one case is considered epidemic’
Epidemic curve rises and falls sharply
Clustering of cases within a short period of time
Person-to-person transmission
All cases usually develop within one incubation period