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					                                      Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report     2008 

 


                                                                 Outbreak Investigations

Surveillance and Outbreak Investigations
   Health professionals are required by law to report selected infectious diseases (excluding
STD, HIV and TB) to the Louisiana Office of Public Health Infectious Disease Epidemiology
Section (IDES). Section epidemiologists look at the number of cases, their location and numer-
ous other characteristics to study the distribution of these diseases and to draw some conclusions
that guide the communicable disease control programs. This allows for the implementation of
important preventive measures such as chemoprophylaxis to prevent invasive disease in close
contacts of cases with meningococcal disease. Furthermore, section epidemiologists work closely
with regional Disease Surveillance Specialists (DSS) for timely and accurate follow-up on
suspected and confirmed cases.
   Disease outbreaks are identified by the reportable disease surveillance system or by reports
from the public or health professionals. Outbreak investigations have been expanded beyond the
usual foodborne outbreaks to include arthropod-borne diseases, hospital acquired infections and
other infectious disease outbreaks in institutions. Investigations are carried out by regional teams
that are supported by the section’s staff. Regional personnel including Infectious Disease-Rapid
Response Team (ID-RRT) staff are regularly trained by the section.

Outbreak Summary 1950-2008
   Infectious disease surveillance information in Louisiana is available from 1950 until the
present day. From 1950 to 2008, there were a total of 700 recorded outbreaks in Louisiana.
(Figure 1)

                                          Figure 1: Summary of total recorded outbreaks – Louisiana, 1950-2008
                                60
                                                       Number of Outbreaks
    Total Number of Outbreaks




                                50
                                                       Linear (Number of Outbreaks)
                                40
                                                                                              y = 0.365x + 0.907
                                30

                                20

                                10

                                0
                                     50    53   56   59    62    65    68    71    74    77    80   83    86    89    92    95       98   01   04   07
                                                                                           Year


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              Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 
    The number of outbreaks has steadily increased in the 58-year span; however this could be
partly due to improved surveillance and reporting rather than an actual increase in the number of
outbreaks. Referring to the peak in 2005, 60 percent of the outbreaks occuring that year were
during the month of September, coinciding with the aftermath of Hurricane Katrina; 31 percent
of those were foodborne.
   Outbreaks observed in the past 58 years in Louisiana have been primarily categorized by
transmission type. For analyses purposes, 14 categories have been designated. Foodborne/enteric
outbreaks have been by far the most common type of outbreak in Louisiana, accounting for 50
percent of the total outbreaks observed from 1950 to 2008. Respiratory outbreaks are the second
most common (9%), and the remaining types of outbreaks account for 8 percent or less of the
total observed outbreaks. (Table 1)


          Table 1: Number of outbreaks, by category and decade – Louisiana, 1950-2008
                   1950-1959     1960-1969     1970-1979      1980-1989     1990-1999      2000-2008          Total
Foodborne/             19            53             56            47             77           140            392(50%)
Enteric
Respiratory             2             0              5            26             17            20            70 (9%)
Other                   2             3              6             7              6            41            65 (8%)
Hepatitis               3             9             21            13             16            2             64(8%)
SSTI*                   0             7              6             3              7            12            35 (5%)
Parasite                0             1              1            10              1            6             19 (2%)
MMRV &                  0             0             9              2             1              6            18 (2%)
Other**
Zoonotic                5             1             5              1             2              0            14(2%)
HAI***                  0             1             1              5             1              2            10 (1%)
Fungal                  0             1             0              0             0              3             4 (1%)
Arbovirus               0             0             2              0             1              0             3 (1%)
Waterborne              1             0             2              0             0              0             3 (1%)
Oral-Fecal              0             0             0              0             0              2            2 (<1%)
Chronic                 1             0             0              0             0              0            1 (<1%)
    Total              33            76            114           114            129           234              700
        * SSTI: Skin and soft tissue infection
        ** MMRV & Other: measles, mumps, rubella, varicella and other related infections;
        ***HAI: hospital-acquired infection




  The number of foodborne/enteric outbreaks has showed the greatest increase since 1950.
Outbreaks of respiratory diseases were low until the 1980’s, when lab diagnostics and detection
improved. Prior to 2000, the majority of hepatitis outbreaks were attributed to hepatitis A. Due to
better control efforts, incidence has been decreasing. Skin and soft tissue infection (SSTI)
outbreaks had remained low until recent years and since, have been on the rise due to the
increase in Methicillin-Resistant Staphylococcus Aureus (MRSA) skin infections. (Figure 2)




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                                Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 

Figure 2: The most common outbreaks, by transmission type and decade - Louisiana, 1950-2008

                          160

                          140                Foodborne
                                             Hepatitis
                          120
                                             Other
    Number of Outbreaks




                          100                Respiratory
                                             SSTI
                          80

                          60

                          40

                          20

                           0
                                  1950-1959         1960-1969       1970-1979        1980-1989       1990-1999       2000-2008

                                                                             Years




    The types of facility in which outbreaks occur often vary by the transmission mode of the
disease. However, a commonality between all of these facilities is that they allow for large
numbers of people to come in close contact with each other at any given point. This environment
is conducive for diseases to spread. (Tables 2 and 3)




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             Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 

           Table 2: Foodborne, Respiratory, Hepatitis and SSTI outbreaks, by facility type
                                       Louisiana, 1950-1999

                          Foodborne         Respiratory       Hepatitis         SSTI             Total
Facility Type             Outbreaks         Outbreaks         Outbreaks       Outbreaks        Outbreaks
                           #       %*         #       %*       #      %*       #      %*        #      %**
School                    44       11%        0       0%      13     20%       2      6%       59       8%
Day Care                   8       2%         21     30%      14     22%       0      0%       43       6%
Nursing Home/ Res.
Facility                   6       2%         8      11%       1      2%       9      26%      24       3%
Restaurant                17       4%         0       0%       1      2%       0      0%       18       3%
Household/Private
Party                     22       6%         2       3%       0      0%       1      3%       25       4%
Hospital/Clinic           12       3%         4       6%       1      2%       3      9%       20       3%
Prison                    16       4%         0       0%       3      5%       0      0%       19       3%
Shelter                    0       0%         0       0%       0      0%       0      0%        0       0%
Company Gathering          9       2%         1       1%       0      0%       0      0%       10       1%
Hotel                      2       1%         1       1%       1      2%       0      0%        4       1%
Other                     31       8%         6       9%       2      3%       1      3%       40       6%
Unknown                   87       22%        7      10%      26     41%       7      20%      127     18%
Total                    254      65%       50     71%    62     97%      23   66%       389     56%
* Percent of total number of FB outbreaks (n=392), respiratory outbreaks (n=70), hepatitis outbreaks
   (n=64), and SSTI outbreaks (n=35) from 1950-2008, respectively
** Percent of total number of outbreaks from 1950-2008 (n=700)




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             Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 

           Table 3: Foodborne, Respiratory, Hepatitis and SSTI outbreaks, by facility type
                                       Louisiana, 2000-2008

                              Foodborne        Respiratory        Hepatitis          SSTI             Total
Facility Type                 Outbreaks        Outbreaks          Outbreaks        Outbreaks        Outbreaks
                               #       %*        #       %*       #       %*        #      %*         #     %**
School                        18       5%        6       9%       0       0%        2      6%        26      4%
Day Care                      10       3%        0       0%       0       0%        0      0%        10      1%
Nursing Home/ Res.
Facility                      20       5%        2       3%       0       0%        0      0%        22      3%
Restaurant                    22       6%        0       0%       1       2%        0      0%        23      3%
Household/Private
Party                         12       3%        0       0%       0       0%        1      3%        13      2%
Hospital/Clinic                2       1%        6       9%       0       0%        1      3%         9      1%
Prison                         9       2%        0       0%       0       0%        1      3%        10      1%
Shelter                       20       5%        2       3%       0       0%        1      3%        23      3%
Company Gathering              1       0%        0       0%       0       0%        2      6%         3      0%
Hotel                          3       1%        0       0%       0       0%        0      0%         3      0%
Other                         20       5%        4       6%       0       0%        4      11%       28      4%
Unknown                        3       1%        0       0%       1       2%        0      0%         4      1%
Total                         140    36%      20     29%      2      3%      12     34%        174 25%
* Percent of total number of FB outbreaks (n=392), respiratory outbreaks (n=70), hepatitis outbreaks (n=64),
   and SSTI outbreaks (n=35) from 1950-2008, respectively
** Percent of total number of outbreaks from 1950-2008(n= 700)



1-Foodborne/Enteric Outbreaks
   Foodborne illness results from the consumption of foods contaminated with biological
pathogens or toxins. The symptoms can include nausea, vomiting, abdominal pain, diarrhea,
fever, headache and fatigue. In Louisiana, there have been 392 reported foodborne/enteric
outbreaks from 1950 through 2008.
   From 1950 through 1999, the majority of foodborne outbreaks occurred in schools, house-
holds/private parties, restaurants and prisons (Table 2). Since 2000, restaurants, hurricane
shelters, nursing homes and schools have been the focal facility types where foodborne outbreaks
have been concentrated (Table 3). The average number of cases per outbreak from 1950 to 2008
has been 42 persons with a range from one to 870 cases per outbreak.
   The most common etiologic agents of foodborne/enteric outbreaks are Norovirus, Salmonella
spp., Shigella spp. (typically sonnei), Clostridium perfringens and Staphylococcus aureus,
respectively. (Figure 3)


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                                   Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report     2008 

 
                               Figure 3: Most common etiologic agents of foodborne/enteric outbreaks, by decade
                                                           Louisiana, 1950-2008

                          45
                          40              Norovirus
                                          Salmonella
                          35
    Number of Outbreaks




                                          Shigella
                          30              C. Perfringens
                          25              Staph FB
                          20
                          15
                          10
                          5
                          0
                                    1950-59          1960-69          1970-79          1980-89          1990-99          2000-08
                                                                                Year




    Norovirus has accounted for 17 percent of all foodborne/enteric outbreaks since 1950,
followed closely by Salmonella spp., accounting for 14 percent of the foodborne outbreaks.
Figure 3 demonstrates the result of improved diagnostics and surveillance capabilities over the
past few decades, which could account for the large increases in Norovirus and C. perfringens.
Foodborne S. aureus has decreased since 1990, possibly due to better control efforts; outbreaks
of Salmonella spp. have remained relatively stable.
   Although the occurrence of foodborne/enteric outbreaks is spread across the state, the
majority have been concentrated in Orleans & Jefferson Parishes (27% of total foodborne/enteric
outbreaks). (Figure 4)




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             Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 
        Figure 4: Location of foodborne/enteric outbreaks, by parish – Louisiana, 1950-2008




   The incidence of foodborne/enteric outbreaks in Louisiana has ranged from 0.07 to 0.17 out-
breaks per 100,000 population by region/parish from 1950 through 1999 and ranged from 0.12 to
0.83 outbreaks per 100,000 population by region/parish from 2000 through 2008. Lafayette
parish and Region 2 exhibited the greatest increase of rates between 1950 to1999 and 2000 to
2008. (Table 4)


Table 4: Location of foodborne/enteric outbreaks, by parish and decades – Louisiana, 1950-2008

                                   1950-1999                            2000-2008
                                                                                                        Rate of
                           Number of                            Number of                            Change/100,000
                                        Rate/100,000                           Rate/100,000
    Parish or Region       Foodborne                            Foodborne                              Population
                                         Population                             Population
                           Outbreaks                            Outbreaks
Region 1                       78               0.17                 39                0.47                 0.30
East Baton Rouge               14               0.10                 9                 0.24                 0.14
Region 2 (excl. East
                               10               0.14                 15                0.83                 0.69
Baton Rouge)
Region 3                       20               0.14                 12                0.35                 0.21
Lafayette                       4               0.07                 13                0.78                 0.71
Region 4 (excl.
                               12               0.08                 6                 0.18                 0.10
Lafayette)
Region 5                        8               0.07                 3                 0.12                 0.05
Region 6                       12               0.09                 11                0.38                 0.29
Region 7                       12               0.10                 9                 0.19                 0.09
Region 8                       13               0.08                 8                 0.25                 0.17
Region 9                       23               0.18                 9                 0.21                 0.03
Unknown                        35                --                  6                  --
       Total                  252               0.14                140                0.35                 0.21


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              Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report         2008 

 

   Foodborne/enteric outbreaks do show a seasonal transmission pattern: there are peaks
observed in April and September. Sixteen of the 41 outbreaks occurring in the month of
September were in 2005, after Hurricane Katrina. January and February experience the lowest
number of foodborne outbreaks. (Figure 5)


    Figure 5: Seasonal transmission patterns of foodborne/enteric outbreaks – Louisiana 1950-2008

                                    50
                                    45                      43
                                                                                         41
                                    40
              Number of Outbreaks




                                    35
                                    30
                                    25
                                    20
                                    15
                                    10
                                    5
                                    0
                                         Jan.   Feb. Mar.   Apr. May   June July   Aug. Sep.   Oct.   Nov. Dec.

                                                                        Month




 The time between infection and first onset of symptoms is known as the incubation period. This
can vary between different organisms. Foodborne S. aureus causes illness quickly by emitting an
enterotoxin once consumed. The observed mean incubation period for outbreaks due to S. aureus
lasted no more than 11 hours. Clostridium perfringens also emits an enterotoxin after ingested.
Figure 6 shows that mean incubation periods for C. perfringens lasted less than one day. The
remaining pathogens’ incubation periods show greater variations.




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                                                        Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 
                       Figure 6: Mean incubation periods of most common etiologic agents of foodborne/enteric
                                                 outbreaks – Louisiana, 1950-2008

                                                   25
                                                                                                                                 Salmonella
                                                   20                                                                            Shigella
                             Number of Outbreaks




                                                                                                                                 Norovirus
                                                   15                                                                            C. Perfringens
                                                                                                                                 Staph-Foodborne
                                                   10


                                                   5


                                                   0
                                                               0-11            12-23           24-35            36-47           48-59            60+

                                                                                                    Hours




   The reported average duration of enteric symptoms per case for each outbreak lasted typically
between 12 hours to 2.5 days after onset of illness. However, some cases reported symptoms
lasting for up to nine days. (Figure 7)

Figure 7: Mean duration of illness in foodborne/enteric outbreaks – Louisiana, 1950-2008

                             25

                                                                                                                                   Duration Mean
    Number of of Outbreaks




                             20


                             15


                             10


                                      5


                                      0
                                                        0-4      5-11     12-23   24-35     36-47      48-59   60-71    72-83   84-95    96-107 108-144 145-216

                                                                                                       Hours




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              Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

  
 Hospitalizations and Death
    Out of the 392 reported foodborne/enteric outbreaks in Louisiana from 1950-2008 with a
 known hospitalization status, 90 percent (243) of the outbreaks did not involve any patient
 hospitalizations. In addition, 99 percent of the reported foodborne/enteric outbreaks with a
 known death status did not result in death; three outbreaks resulted in deaths.

 2-Respiratory Outbreaks
    Respiratory illnesses are easily transmitted to those in close contact due to respiratory droplets
 produced from coughing, sneezing and talking. Improper hand washing and sharing personal
 items with ill persons can also lead to disease transmission. In Louisiana from 1950 through
 2008, there have been a reported total of 70 respiratory-related outbreaks.
    The main etiologic agents of respiratory-related outbreaks in Louisiana during this time
 period are Haemophilus influenzae, Neisseria meningitidis, Streptococcus spp., Influenza Type
 A, Legionella pneumophila and Bordetella pertussis, respectively. H. influenzae has accounted
 for 20 percent of the total number of respiratory-related outbreaks, followed closely by N.
 meningitidis at 17 percent. (Table 5)


             Table 5: Most common etiologic agents of respiratory outbreaks, by decade
                                     Louisiana, 1950-2008
                       1950-59       1960-69      1970-79 1980-89            1990-99       2000-08         Total
Etiologic Agent
                                                        Number                                              Percent
H. influenzae              0             0           1      12                    1            0        14   20%
N. mengingitidis           0             0           0       7                    3            2        12   17%
Streptococcus              1             0           0       0                    1            6         8   11%
Influenza Type
                           0             0             0            2             3            2         7      10%
A
Legionella                 0             0             1            1            2             1         5       7%
Pertussis                  0             0             0            3            0             2         5       7%
Other                      1             0             3            1            7             7        19      27%
Total                      2             0             5           26            17            20       70     100%


    There has been a sharp decrease in the number of H. influenzae outbreaks since the 1980’s
 due to the advent of the Hib vaccine in 1985. In 1987, the vaccine was reformulated to be
 effective in children under 18months of age; the current Hib vaccines are safe in children as
 young as six weeks old. Since Hib vaccines were introduced, the incidence of invasive Hib
 disease in infants and children has fallen by 99 percent.
    Thirty percent of the respiratory-related outbreaks in Louisiana occurred in day care facilities
 prior to 2000, along with an additional 17percent occurring in nursing homes and hospitals/
 clinics. (Table 2) From 2000-2008, respiratory-related outbreaks have mainly occurred in
 schools and hospitals/clinics. (Table 3) The average number of cases per outbreak from 1950-
 2008 was 16 persons with a range from one to 275 cases per outbreak.

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                               Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report     2008 

 
  Respiratory outbreaks have been largely concentrated in Jefferson and Orleans parishes, as
well as in East Baton Rouge (Figure 8).


                          Figure 8: Location of respiratory-related outbreaks, by parish – Louisiana, 1950-2008




   The seasonal trend of the number of respiratory-related outbreaks over the past 58 years,
shows a peak in the month of May and has been lowest in the months of April and July.
September through January exhibit a similar number of respiratory-related outbreaks. (Figure 9)

                               Figure 9: Seasonal transmission of respiratory-related outbreaks, by month
                                                         Louisiana, 1950-2008

                          12
    Number of Outbreaks




                          10
                           8
                           6
                           4
                           2
                           0
                                Jan.   Feb.    Mar.    Apr.    May     June     July    Aug.    Sep.    Oct.    Nov.    Dec.
                                                                          Month



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             Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 
Hospitalizations and Death
    Of the 70 reported respiratory-related outbreaks between 1950 and 2008, 30 percent did not
lead to any hospitalizations of its cases compared to 13 percent of the outbreaks which did. The
remaining 57 percent of outbreaks did not have a hospitalization status listed. Eighty-one percent
of the total reported respiratory-related outbreaks did not lead to any deaths of its cases,
compared to 17 percent of the outbreaks which did lead to case fatalities.

3-Hepatitis Outbreaks
   Hepatitis is a viral disease which affects the liver and is the leading cause of liver cancer. In
the United States, hepatitis is most commonly due to types A, B, C and less commonly, due to D
and E. Depending on the type of hepatitis virus, the transmission can vary. Types A and E are
typically transmitted via the fecal-oral route, type B via blood and other bodily fluids and type C
mostly via blood.
   From 1950, there have been a total of 64 reported outbreaks of hepatitis in Louisiana.
Although the virus type of most of these are unknown, particularly prior to the advent and
improvement of laboratory diagnostics, the remaining hepatitis outbreaks have been caused by
types A, B and E. Type A has been the leading single most common cause of hepatitis
outbreaks, accounting for 95 percent of the total reported hepatitis outbreaks. The majority of
Hepatitis A outbreaks occurred from 1970 to79 (n=20). Since 2000, there has only been one
Hepatitis A outbreak. Type B has only accounted for two outbreaks in the 1970’s and 80’s. Type
E accounted for one outbreak in 2007.
   Prior to 2000, day cares and schools constituted 42 percent of the hepatitis outbreak locations-
likely due to fecal-oral transmission among children (Tables 2 and 3). Hepatitis outbreaks from
1950-2008 have ranged from one to 72 persons with an average case number of 9.6 persons per
outbreak.
   St. Tammany, Tangipahoa, Lafayette, Orleans and Jefferson parishes exhibit the most
concentrated locations of hepatitis outbreaks from 1950 through 2008. (Figure 10)

            Figure 10: Location of hepatitis outbreaks, by parish – Louisiana, 1950-2008




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                                  Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report     2008 

 
                   The seasonal trend of hepatitis outbreaks show peaks in June and September. (Figure 11)


                          Figure 11: Seasonal transmission of hepatitis outbreaks, by month – Louisiana, 1950-2008

                           10
                                                                                                    9
                            9
                            8
    Number of Outbreaks




                            7
                                                                           6
                            6
                            5
                            4
                            3
                            2
                            1
                            0
                                Jan.    Feb.     Mar.    Apr.    May     June     July    Aug.    Sep.     Oct.    Nov.    Dec.
                                                                            Month



Hospitalizations and Deaths
   Three of the 64 total hepatitis outbreaks resulted in a total of 6 persons hospitalized. None of
these 64 outbreaks resulted in case fatalities.

4-SSTI: Skin and Soft Tissue Infections
    From 1950, all of the outbreaks related to skin and soft tissue infections have been caused by
the bacterium Staphylococcus aureus. However, beginning in 1991, outbreaks caused by the
strain of Staphylococcus aureus which is resistant to methicillin drugs (commonly called
“MRSA”) were identified. Out of the 35 total reported SSTI outbreaks in Louisiana, seven (20%)
are known to have been caused by MRSA and four are suspected to have been caused by MRSA.
   The single most common type of facility where SSTI outbreaks have occurred are nursing
homes/residential facilities, accounting for 26 percent of the total number of SSTI outbreaks in
Louisiana from 1950 through 1999. Hospitals/clinics as well as schools were also the major
location of SSTI outbreaks prior to 2000 (Table 2). Since 2000, schools and company gatherings
have been the main location types of SSTI outbreaks (Table 3).
   The majority of SSTI outbreaks have occurred in Rapides and Orleans parishes. Otherwise,
there does not appear to be a pattern of SSTI outbreaks across the state. (Figure 12)




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                                Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 

                                Figure 12: Location of SSTI outbreaks, by parish – Louisiana, 1950-2008




   September and May appear to be the peak months of the year for SSTI outbreaks. Trans-
mission is relatively low and stable the rest of the year. (Figure 13)



                          Figure 13: Seasonal transmission of SSTI outbreaks, by month - Louisiana, 1950-2008


                           8
                           7
    Numver of Outbreaks




                           6
                           5
                           4
                           3
                           2
                           1
                           0
                               Jan.      Feb.      Mar.      Apr.      May       June      July      Aug.      Sep.       Oct.     Nov.   Dec.
                                                                                     Month




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             Louisiana Office of Public Health – Infectious Disease Epidemiology Section – Annual Report    2008 

 
Hospitalizations and Death
   Of the 35 total SSTI-related outbreaks from 1950 in the state of Louisiana, five of these
outbreaks resulted in hospitalizations (n=39 persons total). One outbreak resulted in case fatality.

4-Other
   There were 65 outbreaks caused by various other etiologic agents or unknown etiologic
agents. (Table 6)

    Table 6: Etiologic agents/illness types of other outbreaks, by decade – Louisiana, 1950-2008

        Etiologic
                               1950-59      1960-69       1970-79      1980-89       1990-99      2000-08       Total
    Agent/Illness Type
Anaphylaxis                        0             0            0             1            0             0             1
Asphyxia                           0             0            1             0            0             0             1
Cancer                             0             0            0             1            0             0             1
Chemical                           0             0            0             2            0             2             4
Herpes Simplex Virus               0             0            0             0            0             1             1
Hysteria                           0             0            2             0            0             2             4
Metal                              0             0            1             0            0             0             1
Miscarriages                       0             0            0             1            0             0             1
Neuromyasthenia                    1             1            0             0            0             0             2
Pesticides                         0             1            1             0            1             0             3
Suicide                            0             0            0             0            1             0             1
Syphilis                           0             0            1             0            0             0             1
Tetanus                            1             0            0             0            0             1             2
Toxic                              0             0            0             1            0             1             2
Zinc                               0             1            0             0            0             0             1
Unknown                            0             0            0             1            4            34            39
Unknown-
                                   0             0            0             1            4            29            34
Gastroenteritis
Unknown-Respiratory                0             0            0             0            0             1            1
Unknown-Rash                       0             0            0             0            0             4            4
          Total                    2             3            6             7            6            41            65


  The period 2000 through 2008 exhibited the most outbreaks in this classification. The most
common of these were due to unknown agents leading to gastroenteritis. Hysteria, chemicals,
unknown agents leading to rash and pesticides also contributed to a major portion of outbreaks
under this classification.




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