Maricopa County
Department of Public Health

2005 Outbreak Report

Submitted By

Division of Epidemiology/Data Services

August 23, 2006

The purpose of this report is to provide a general overview of the disease outbreak
investigations that were reported during 2005 in Maricopa County, Arizona. For a more detailed
description on the methodology followed in the investigation of outbreaks, please see the 2004
Outbreak
Summary
Report
on
the
website:
http://www.maricopa.gov/public%5Fhealth/epi/outbreak.asp

Reporting requirements
In Arizona, health care providers (HCP), health care institutions (HCI), correctional facilities
(CF), childcare establishments (CCE), administrators of schools, and shelters are all required to
report outbreaks of infectious diseases to the Local Public Health Authority (see Table 1) under
Arizona Administrative Code A.A.C. R9-6-203 and ARS Title 36.
Table 1. Diseases requiring outbreak notification within 24 hours

Disease/Condition
Amebiasis
Campylobacteriosis
Conjunctivitis: acute
Cryptosporidiosis
Diarrhea, Nausea, or Vomiting
Giardiasis
Hepatitis A
Hepatitis E
Salmonellosis
Scabies
Shigellosis
Streptococcal Group A Infection
Taeniasis
Vibrio Infection
Yersiniosis

Reporting by
HCPs, HCIs,
and CFs
X
X
X
X
X
X
X
X
X
X
X

Reporting by Schools,
CCEs, and Shelters

X
X

X
X

X
X
X

Results
In 2005, 66 outbreaks were investigated by the Maricopa County Department of Public Health
(MCDPH). The following sections summarize these data. For comparison purposes, 2004 data
from 38 outbreaks and 2003 data from 41 outbreaks have been included.
Note: This report brings together several documents previously distributed and/or presented in other
venues.

1

In 2005, 66 outbreaks were reported to MCDPH, or an average of 5.5 per month with a range of
2-13 per month. In 2004, the total was 38, an average of 3.2 per month, with a range of 0-2 per
month. In 2003, the total was 41, an average of 3.4 per month, with a range of 1-7 per month.
In 2005, the month of May had the most outbreaks reported with 13; while in 2004 the month
with the highest number of outbreaks was December with 12 (see Figure 1).
Figure 1. Number of Outbreaks Reported by Month 2003-2005
14
2003 (n=41)

2004 (n=38)

2005 (n=66)

Number of Outbreaks

12
10
8
6
4
2

No
ve
m
be
r
De
ce
m
be
r

Oc
tob
er

Se
pt
em
be
r

Au
gu
st

Ju
ly

Ju
ne

M
ay

Ap
ril

M
ar
ch

Fe
br
ua
ry

Ja
nu
ar
y

0

Month of Report

The median number of persons affected per outbreak in 2005 was 7 (range 2-138); while in
2004 the median number of persons affected per outbreak was 10 (range 2-390); and the
median number affected was 13 (range 2-800) in 2003. In 2005, 80% of outbreaks involved
fewer than 20 persons (see Figure 2).
Figure 2. Number of Persons Affected Per Outbreak 2003-2005
25
2003 (n=41)

2004 (n=38)

2005 (n=66)

Number of Outbreaks

20

15

10

5

0
<5

5-10

11-20

21-50

51-100

101+

Num ber of Persons Affected

2

In 2005, the percentage of all outbreaks of unknown etiology was 50%, in 2004 this was 37%,
and in 2003, this percentage was 39%. All 33 outbreaks of unknown etiology in 2003, 1004,
and 2005 were gastrointestinal in nature. The pathogen of interest remained unknown for a
variety of reasons including failure to obtain specimens for testing, outbreaks which were
reported too late for testing, and testing which did not identify a pathogen. Table 2 summarizes
the number of outbreaks by pathogen for the past three years.
Table 2. Number of Outbreaks by Etiology
Etiology of Outbreaks

2003

Aseptic Meningitis
H. pylori
Head Lice
Conjunctivitis
Giardia
Influenza
Influenza-like Illness
Legionella
MRSA
Pneumonia
Parvovirus B 19 (5th Disease)
Strep Group A
Salmonella
Streptococcus
Strep pneumonia
Shigella
Viral Gastroenteritis
Scabies
Varicella
Norovirus
Unknown (GI)
Total

2004

1
0
0
1
2
2
2
1
1
1
0
1
3
1
0
4
0
1
0
4
16
41

0
1
1
0
0
0
0
0
0
0
0
0
1
0
0
1
1
4
3
12
14
38

2005
0
0
1
2
0
2
3
0
0
1
1
0
0
0
1
1
0
6
2
13
33
66

While a specific etiology is often not determined, most outbreaks can be broadly classified.
From 2003 through 2005, the majority of outbreaks were gastrointestinal in nature (see Table
3). Other types of outbreaks include conjunctivitis, streptococcal infections, head lice, and
MRSA.
Table 3. Type of Outbreaks
Outbreak Type

2003

2004

2005

Gastrointestinal

29

30

47

Respiratory

6

0

7

Rash

2

7

9

Other

4

1

3

Total

41

38

66

3

As shown in Figure 3, more schools and assisted living/long term care facilities reported
outbreaks in 2005 compared to previous years. Twice as many restaurant outbreaks were
reported in 2005 than in 2004.
Figure 3. Outbreaks Reported by Type of Facility 2003-2005
2003 (n=41)

2004 (n=38)

2005 (n=66)

25
20
15
10
5

Facility Type

R
es
ta
ur
an
In
di
t
vi
du
al
s/
O
th
er

P
ris
on
/J
ai
ed
l
Li
vi
ng
/L
TC
F
A
ss
is
t

W
or
ks
ite

H
ot
el
/R
es
or
t

H
os
pi
ta
l

S
ch
oo
ls

0

C
at
D
ay
er
er
ca
re
/C
hi
ld
ca
re

Number of Outbreaks Reported

30

As indicated in Figure 4, gastrointestinal (GI), respiratory and rash collectively accounted for
~94% of all outbreaks reported in 2005. GI outbreaks were prevalent in all but jail facilities,
accounting for 71% of the total outbreaks reported. As expected, the GI outbreaks were
predominately reported by food establishments. Hospital/hospice/rehabilitation centers and
long term care/assisted living centers were more likely to report all types of outbreaks.
Category “Other” in Figure 4 includes head lice and conjunctivitis outbreaks.
Figure 4. Number of Outbreaks by Type and Facility Reported in 2005
(n=66)
30
Influenza

Rash

GI

Respiratory

Other

Number of Outbreaks

25
20
15
10
5

R
es
or
t

C
ar
e
Te
rm

Ja
il

*

Lo
ng

Fo
od

E

st
ab
lis

H
os
pi
ta
l

hm
en
t

ch
oo
l
/S
D
ay
ca
re

C
at
er

er
/

Pa
rty

Pl
ac
e

0

Facility

*Hospital includes hospitals, hospice and rehabilitation centers.

4

Figures 5 – 7, illustrates the occurrences of GI, rash, and respiratory outbreaks by percentages
and number of outbreaks by facility.
Figure 5. Percentage of GI Outbreaks per Facility 2005
n=47
Long Term Care/

Resort

Caterer / Party Place

Senior

2% (1)

4% (2)
Day care / School

15% (7)

13% (6)

Hospice/Hospital/
Rehab&Care Center
6% (3)

Food Establishment
60% (28)

Figure 6. Percentage of Rash Outbreaks per Facility 2005
n=9
Long Term Care /

Day care / School

Senior

22% (2)

45% (4)

Jail
22% (2)

Hospice/Hospital/
Rehab&Care Center
11% (1)

Figure 7. Percentages of Respiratory Outbreaks per Facility
2005, n=7
Long Term Care/
Senior
33% (2)

Day care / School
50% (3)

Hospice/Hospital/
Rehab&Care Center
17% (2)

5

For 16 (34%) of the 47 gastrointestinal (GI) outbreaks in 2005, stool specimens were collected
for testing at the Arizona State Laboratory. The number of specimens collected per outbreak
ranged from 1 to 16. The total number of outbreak-related specimens collected in 2005 was 78.
Of these 78 specimens, 68 (87%) were tested. Once a pathogen is identified in an outbreak,
the lab may not test all specimens submitted on the same outbreak. Figure 8 shows the
distribution of specimens submitted and tested for 2005.
The majority of specimens (n=61) were tested for Norovirus, of those, 38 (62%) were positive.
The remaining seven specimens were tested for Salmonella, Shigella and Campylobacter; all
were negative. As shown in Figure 8. Specimens were not collected for all GI outbreaks.
Reasons for not collecting specimens include too much time elapsing between the event and
the report of illness and uncooperative or hard to reach cases.
Figure 8. Specimens submitted and tested by month
2005

35

Number of GI outbreaks
30

Number of specimens submitted
Number of specimens tested

Number

25
20
15
10
5
0
Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sept

Oct

Nov

Dec

Summary
In 2005, there were 66 outbreaks investigated in Maricopa County. The average number of
outbreaks reported per month was six. The outbreaks ranged in size from 2 to 138 persons
affected. In 2005, the month with the highest number of outbreaks was May. Most reported
outbreaks affected 5-10 persons. By far the most common pathogen isolated in outbreaks was
norovirus; however, 50% of outbreaks were of unknown etiology. Environmental Services
reported the majority of outbreaks which stemmed primarily from restaurant complaints. Most
investigations involved restaurants followed by nursing homes or long-term care facilities.

6