Which of the following can cause an increase in the prevalence of the disease -
Derived Factors that increase Prevalence 

Prevalence increases with addition of diseased people (immigration)
Prevalence increases with subtraction of healthy people (emigration)
Prevalence increases with prolongation of life in chronic diseases
Prevalence increases with decreased death rate amongst diseased

Derived Factors that decrease Prevalence 

Prevalence decreases with addition of healthy people (immigration)
Prevalence decreases with subtraction of diseased people (emigration)
Prevalence decreases with increased cure rates
Prevalence decreases with increased death rates
Prevalence decreases with preventive programs such as immunization (which prevent new cases from occurring).
Immigration of healthy persons
Increased cure rate of disease
Longer duration of illness
Decrease in population