(NYS Dept. of Health)
1918 Flu Epidemic
32
Case Fatality Rate (CFR)
•
Formula:
•
# of case patients
x 100
# of cases reported
•
It answers what percent o
f people diagnosed as
having a certain disease die within a certain time
after diagnosis.
•
If 25 of every 100 (25 ÷100=.25 x 100 =25%)
persons
diagnosed with lung cancer
die in 5 years the CFR is
25%.
•
The 5 year survival rate is 1  .25
= (.75 ) or 75 %
33
Morbidity Rates
34
Let’s resume.. VNA Case Study
•
Refer to page 123
•Since the epidemic began, 107,980 cases of HIV/AIDS have been diagnosed in Florida.•Nearly half (48%) have occurred in African American people.•What information does Lindsay need to understand the scope of the problem in the two counties?
•
Refer to page 124
•There are 2,150 people living with HIV/AIDS•What is the crude rate of the HIV/AIDS burden in these two counties?
35
Incidence Rate
•
The number of
new
cases at a particular point or
period of time
•
Calculated in a similar way to mortality rates
Example: Flu in VA
•
From Jan 1 –Dec 31 2014 there were
500 cases of
influenza dx in
Virginia; Population is 8,000,000.
# of newly diagnosed cases in a certain time period
divided
by # at risk of disease in population X 100,000
500 ÷8,000,000= .0000625 X 100,000 = 6.25 new cases of
influenza per 100,000 in 2014
36
VNA Case Study
•
Page 126
•Lindsay finds that 384 new cases of HIV infection were dx in the 2 counties within the last year. •What is the incidence rate?•Contrast this incidence rate with:•The crude rate calculated on page 124 and •The incidence rate in the US 83.7 new HIV infections per 100,000 in one year.
37
Attack Rates
•
The
attack rate
(AR) is a special incidence rate
used in investigations of disease outbreaks.
Often used with food borne illness outbreaks
and during an epidemic
•
Number of people at risk who develop a certain
illness/Total number of people at risk.
•
Example: Age groups with high ARs are at
increase risk of disease
Number of people at risk who develop the disease
Total number of people at risk
X
100
=
Your turn: the picnic problem
Attack rate calculation
•
226 people ate chicken salad at the picnic
•
176 people developed acute GI symptoms
•What is the attack rate?
Prevalence
•
Prevalence

all
(old + new)
the people with a
given health condition at a particular point or
period of time
•
it’s a proportion of the population that has a
certain disease at one point in time
•
Influenced by 2 factors
•
Number of people with condition in past
•
Duration of illness
•
It is expressed as a percent
•
Explain:
•
Period
•
Point Prevalence
40
A way to think about
prevalence:
41
Prevalence
•
Number of existing cases
of
a disease at one
point in time ÷ total number of population X 100.
•
In NJ there were 10,000 people with CHF
and the
population was 700,000.
•
10,000 ÷ 700,000 X 100 = 1.4 % of the population
has CHF
•
So the prevalence of CHF in NJ is 1.4%
42
Now your turn…..
•
Calculate the prevalence of diabetes in Virginia.
•
Number of people with diabetes in 2014 were
531,000
•
The population is 8,326,000.