Maricopa County Department of Public Health 2006 Outbreak Summary Report Submitted By Office of Epidemiology & Data Services January 25, 2007 The purpose of this report is to provide a general overview of the disease outbreak investigations that were reported during 2006 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_Health/EPI/pdf/2004OutbreakReport.pdf. 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. Also, hotel, motels, and resorts are required to report contagious or epidemic diseases occurring in their establishments within 24 hours under Arizona Revised Statutes Title 36, Chapter 6, Article 2. 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 2006, 74 outbreaks were investigated by the Maricopa County Department of Public Health (MCDPH). The following sections summarize these data. For comparison purposes, data from 66 outbreaks that occurred in 2005 and 38 outbreaks that occurred in 2004 have been included. 1 In 2006, 74 outbreaks were reported to MCDPH, or an average of 6.2 per month with a range of 2-10 per month. This represents an increase over the previous two years. In 2005, the total was 66, 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. As shown in Figure 1, the pattern of outbreaks is a bimodal curve with peaks in late spring and winter months. Figure 1. Number of Outbreaks Reported by Month 2004-2006 14 2004 (n=38) 2005 (n=66) 2006 (n=74) 10 8 6 4 2 Se t pt em be r O ct ob er No ve m be De r ce m be r Au gu s Ju ly Ju ne ay M Ap ril ar ch M ry Fe br ua ry 0 Ja nu a Number of Outbreaks 12 Month of Report 2 The median number of persons affected per outbreak in 2006 was 10 (range 2-78); while in 2005 the median number of persons affected per outbreak was 7 (range 2-138); and in 2004 the median number of persons affected per outbreak was 10 (range 2-390). In 2006, 58 of the 74 outbreaks (72%) involved 20 or fewer persons (see Figure 2). Figure 2. Number of Persons Affected Per Outbreak 2004-2006 30 Number of Outbreaks 2004 (n=38) 2005 (n=66) 2006 (n=74) 25 20 15 10 5 0 <5 5-10 11-20 21-50 51-100 101+ Number of Persons Affected 3 In 2006, the percentage of all outbreaks of unknown etiology was 38%. In 2005, this was 50%, and in 2004 this was 37%. Of the 28 outbreaks of unknown etiology in 2006, 26 were gastrointestinal in nature and the remaining two were rash illnesses. 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 2004 2005 2006 Conjunctivitis E. coli O157:H7 Giardia H. pylori Head Lice Hepatitis A Influenza Influenza-like Illness Legionella MRSA Norovirus Parvovirus B 19 (5th Disease) Pneumonia Salmonella Scabies Shigella Staphylococcus (Skin Infections) Strep pneumonia Unknown (GI) Unknown (Rash) Varicella Viral Gastroenteritis 0 0 0 1 1 0 0 0 0 0 12 0 0 1 3 1 0 0 15 0 3 1 2 0 0 0 1 0 2 3 0 0 13 1 1 0 6 1 0 1 33 0 2 0 5 1 1 0 0 1 0 1 0 2 21 0 0 0 7 2 1 0 26 2 4 0 Total 38 66 74 While a specific etiology is often not determined, most outbreaks can be broadly classified based on the symptoms exhibited by cases. From 2004 through 2006, the majority of outbreaks investigated by the MCDPH were gastrointestinal in nature (see Table 3). The “Other” category includes conditions such as conjunctivitis and head lice. Table 3. Type of Outbreaks 2004 2005 2006 Gastrointestinal Respiratory Rash Other Outbreak Type 30 0 7 1 47 7 9 3 51 1 17 5 Total 38 66 74 4 As shown in Figure 3, more outbreaks in schools and daycare centers were reported in 2006 compared to previous years while the number of restaurant outbreaks reported in 2006 declined. Despite this decline, the largest number of reports for any one category were for restaurants, followed by senior living facilities (assisted living/long term care facilities/senior apartments), and then schools. The “Other” category includes caterers and private residences. 30 2004 (n=38) 2005 (n=66) 2006 (n=74) 25 20 15 10 5 O th er ivi ng Re Fa st au cil it y ra nt /F oo d Es t. n/ Ja il Se ni or L Pr iso te W or ks i Sc ho ol s he lt e Ho r sp it a l/ C l in ic Re so r t/ Ho te l 0 Da yc ar e/ S Number of Outbreaks Reported Figure 3. Outbreaks Reported by Type of Facility 2004-2006 Facility Type 5 As indicated in Figure 4, gastrointestinal (GI), respiratory and rash collectively accounted for 69 of 74 (93%) of all outbreaks reported in 2006. GI outbreaks were prevalent in all but jail facilities, accounting for 51 of 74 (69%) of the total outbreaks reported. The GI outbreaks in 2006 were predominately reported in restaurants/food establishments. The “Other” category in Figure 4 includes head lice and conjunctivitis outbreaks. Figure 4. Number of Outbreaks by Type and Facility Reported in 2006 (n=74) 21 GI Respiratory Rash Other 18 15 12 9 6 3 O th er he lt e Ho r sp it a l/ C li n ic Re so r t/ Ho te l Sc ho ol s W or ks ite Pr Se iso ni n/ or Ja Li il vi ng Re Fa st au cil it y ra nt /F oo d Es t. 0 Da yc ar e/ S Number of Outbreaks 24 Facility 6 Figure 5 illustrates the GI outbreaks in 2006 by type of facility. Figure 6 shows rash outbreaks by facility type for 2006. A chart for respiratory outbreaks is not shown as there was only one respiratory outbreak reported in 2006. This one outbreak occurred in a long-term care facility. (The other five outbreaks in 2006 were in the “other” category and are also not shown.) Figure 5. Percentage of GI Outbreaks per Facility 2006 (n=51) Caterer (1) 2% Daycare/Shelter Private (3) 6% Hospital/Clinic Residence (2) (3) 6% 4% Hotel (3) 6% Food Establishment (21) 40% Schools (9) 18% Senior Living Facility (8) 16% Worksite (1) 2% Figure 6. Percentage of Rash Outbreaks per Facility 2006 (n=17) Daycare/Shelter (2)12% LTCF (6) 34% Prison/Jail (1) 6% Hospital/Clinic (2) 12% Schools (4) 24% Worksite (2) 12% 7 Specimens For 34 of 51 (61%) of the gastrointestinal (GI) outbreaks in 2006, specimen kits were provided to cases for a total number of 92 kits and a range of 1-8 kits per outbreak. For 28 of the 51 (55%) GI outbreaks in 2006, stool specimens were received for testing at the Arizona State Laboratory. The total number of specimens collected was 80, the number of specimens collected per outbreak ranged from 1 to 7. Figure 7 shows the distribution of specimen kits provided and specimens submitted and tested in 2006. (NOTE: 10 specimen kits were provided by the hospital or healthcare facility in which the outbreak occurred.) Specimens were not collected for all GI outbreaks. Reasons for not collecting specimens included too much time elapsing between the event and the report of illness and uncooperative or hard to reach cases. Figure 7. Kits Provided and Specimens Received by Month 2006 30 GI Outbreaks Kits Specimens Submitted 25 Number 20 15 10 5 r D ec em be r em be be r N ov ct o m be te O Month Se p Au g us r t ly Ju ne Ju ay M il Ap r ar ch M ry ua Fe br Ja nu ar y 0 The total number of outbreak-related specimens collected in 2006 was 80. The majority of specimens (n=52, 65%) were tested for Norovirus only, of those, 32 (62%) were positive, 18 (35%) were negative, and 2 (4%) were not tested or lost. Specimens were also tested for both Norovirus and bacterial enteric pathogens (Salmonella, Shigella, Campylobacter, and E. coli O157:H7) (n=22). Of those 22 specimens all tested negative for bacterial enteric pathogens and 13 (59%) were positive for norovirus. Of the remaining six specimens, two were tested for bacterial enteric pathogens; all were negative, one specimen was not tested, and three specimens were tested for Shigella; all were negative. Two additional specimen results were received from private labs. Both of these specimens tested positive for Shigella. 8 For all 45 norovirus positive specimens sequencing was obtained. Four specimens were positive for GI.4 strain, one for GII.1, one for GII.15, 31 for GII.4, seven for undetermined GI, and one for undetermined GII. Figure 8 shows the distribution of GII.4 and other norovirus positive specimens by month. Most GII.4 specimens were submitted in the spring and early summer, while most other norovirus positive specimens were submitted in the fall and winter. Figure 8. Number of Specimens Testing Positive for Norovirus GII.4 by Month (n=31) GII.4 Other Norovirus 7 6 5 4 3 2 1 ob N ov er em b D e c er em be r O ct r t m be us Se p Month te ly Au g Ju ne Ju ay M il Ap r nu a F e ry br ua ry M ar ch 0 Ja Number of Specimens 8 9 Outbreaks of norovirus GII.4 (n=14) occurred in all types of facilities, most commonly in restaurant/food establishments and senior living facilities (see Figure 9). This distribution is similar to the distribution for total gastrointestinal outbreaks, although the GII.4 outbreaks were more likely to be associated with senior living facilities (36% of GII.4 outbreaks vs. 16% of total gastrointestinal outbreaks) and less likely to be associated with restaurant/food establishments (29% of GII.4 outbreaks vs. 40% of total GI outbreaks) and schools (7% of GII.4 outbreaks vs. 18% of total GI outbreaks). FIgure 9. Number of GII.4 Norovirus Outbreaks by Facility Other (1, 7% Hotel/Resort (1) 7% Caterer (1) 7% Restaurant/Food Est. (4) 29% Hospital/Clinic (1) 7% School (1) 7% Senior Living Facility (5) 36% 10 The number of persons affected in outbreaks of norovirus GII.4 and other norovirus strains is shown in Figure 10. GII.4 outbreaks were more likely to affect 11-20 persons than were the other norovirus outbreaks. GII.4 outbreaks were somewhat less likely than other norovirus outbreaks to involve a large number of persons (51 to 100 persons). Figure 10. Number of GII.4 Outbreaks by Number of Persons Affected (n=14) Number of Outbreaks 6 GII.4 Other Norovirus 5 4 3 2 1 0 <5 5-10 11-20 21-50 51-100 Number of Persons Affected Summary In 2006, there were 74 outbreaks investigated in Maricopa County. The average number of outbreaks reported per month was 6.2. The outbreaks ranged in size from 2 to 78 persons affected. In 2006, the months with the highest number of outbreaks were March and May. Most reported outbreaks affected 5-10 persons. By far the most common pathogen isolated in outbreaks was norovirus; however, 38% of outbreaks were of unknown etiology. Most investigations involved restaurants followed by senior living facilities. 11