An outbreak of foodborne illness at an Auckland hui

The New Zealand Public Health Report ISSN 1173-0250 Volume 5 Number 5 May 1998 An outbreak of foodborne illness at an Auckland hui Greg Simmons,* Public Health Physician; Kathryn Manning, Health Protection Officer; Auckland Healthcare Public Health Protection An outbreak of 64 cases of gastroenteritis followed an Auckland hui in July 1997. Combined epidemiological and microbiological investigation identified roast pork as the most likely source of infection and Clostridium perfringens as the most likely agent. A number of inadequate food safety procedures, that could have contributed to this outbreak, were identified in a hazard analysis and critical control point assessment. These inadequate procedures included the use of uninspected meat, unrefrigerated transport of the meat, no monitoring of the temperature reached in the meat during cooking, slow cooling at room temperature of the cooked meat, and lack of adequate sanitation of kitchen equipment between uses, especially between use for raw and cooked foods. The promotion of food safety programmes in marae is recommended. On 22nd July 1997, a local general practitioner notified Auckland Healthcare Public Health Protection of a gastroenteritis case. The case had attended a local hui 10 hours before becoming unwell and knew of three other attendees with similar symptoms. The hui had lasted one day, although some of those attending from outside Auckland arrived the previous night. A total of five meals or tea breaks had been catered. Methods A list of attendees was provided by the hui facilitator. A food questionnaire covering all meals (including foods and drinks) served at the hui was compiled and administered to attendees. Statistical analyses were performed as for a retrospective cohort study using EpiInfo Version 6.04b. A case was defined as either diarrhoea, consisting of at least three loose motions in a 24 hour period, or at least two of the following: stomach pains, fever, vomiting, or nausea, within 48 hours of attending the hui. The only food available for sampling at the time of investigation was a frozen, uncooked leg of pork from the same animal served at the hui. Faecal samples were obtained from three cases. The food and faecal samples were tested for Bacillus cereus, Clostridium perfringens, coagulase-positive Staphylococci, Campylobacter, Yersinia enterocolitica, Salmonella, Shigella, and Vibrio. A hazard analysis critical control point (HACCP) assessment was made retrospectively, based on information from the caterer and others involved in the preparation of food served at the hui. In addition, an examination was made of the marae kitchen facilities for food storage and preparation. *Correspondence: Dr Greg Simmons, Auckland Healthcare Public Health Protection, Bag 92605 Symonds St, Auckland. Email: gregs@ahsl.co.nz Results Epidemiological analysis: Eighty-three percent (115/139) of the hui attendees were interviewed. Sixty-four of those interviewed satisfied the case definition; an attack rate of 55.7%. Symptom frequencies are shown in Table 1. Of the 64 cases, only four (6.3%) had consulted a medical practitioner about their illness. Of the five meals or tea breaks at the hui, only the lunch was associated with illness (relative risk [RR] 10.98; 95% confidence interval [CI] 1.63-73.94). Cases were more likely to have consumed Table 1: Symptom frequency among 64 cases of gastroenteritis following an Auckland hui Symptom Number of cases Percent of cases Diarrhoea 59 92.2 Stomach pain 53 82.8 Nausea 24 37.5 Fever 14 21.9 Vomiting 7 10.9 Other 1 12 18.8 1 headache, muscle ache and lethargy Contents An outbreak of foodborne illness at an Auckland hui 33 Surveillance and control notes 35 Surveillance data 38 Public health abstracts 40 Travel health 40 Page 33 The New Zealand Public Health Report Vol. 5 No. 5 May 1998

Table 2. Attack rates and relative risks for hui attendees eating foods served at the lunch Food item Number of persons consuming food Number of persons not consuming food Risk ratio 95% P-value Confidence Cases Non-cases Percent attack rate Cases Non-cases Percent attack rate interval Roast pork 60 27 68.9 3 23 11.5 5.98 2.04-17.49 0.00000023 Steamed cabbage 48 23 67.6 14 26 35.0 1.93 1.23-3.04 0.00090 Kumara 44 22 66.7 19 28 40.4 1.65 1.12-2.43 0.0056 Cold potato salad 37 16 69.8 25 34 42.4 1.65 1.17-2.33 0.0035 Raw mussels 30 12 71.4 33 38 46.5 1.54 1.12-2.10 0.0099 Corned silverside 16 5 76.2 47 45 51.1 1.49 1.09-2.04 0.037 Trifle and cream 33 15 68.8 30 35 46.2 1.49 1.08-2.06 0.017 Seafood coleslaw 21 8 72.4 42 42 50.0 1.45 1.06-1.97 0.036 Roast pumpkin 38 21 64.4 24 28 46.2 1.40 0.98-1.98 0.053 Potato/pumpkin mash 43 26 62.3 20 24 45.5 1.37 0.95-1.99 0.078 Cooked mussels 8 3 72.7 55 47 53.9 1.35 0.90-2.02 0.23 Steamed pudding 7 5 58.3 56 45 55.5 1.05 0.63-1.75 0.85 roast pork at the lunch than non-cases (RR 5.98; 95% CI 2.04-17.49). Cases were also more likely to have consumed the other 11 food items served for lunch, although the risk ratios were much lower than that associated with pork (Table 2). Stratified analysis suggested that the association of three of the other food items (potato/pumpkin mash, cooked mussels, and steamed pudding) with illness could be attributed to confounding by pork consumption, whereas the remaining eight could not. The median incubation time between the lunch and onset of illness was 13 hours (mean 12 hours) with a range 1-31 hours (Figure 1). Symptom duration ranged from 5-96 hours, with a median of 26 and mean of 34 hours. Microbiological investigation: The results of the tests on the faecal samples are shown in Table 3. Culture of the uncooked leg of pork revealed moderate levels of coagulasepositive Staphylococci (1.7 x 10 3 cfu/g) and >1.1 x 10 3 cfu/g of faecal coliforms. HACCP assessment: The pork had been prepared as follows: the loins were rolled and stuffed with a proprietary bread-based herb stuffing, and the forequarters and leg were scored and marinated in a honey-based mixture. The meat was reported to have been cooked in a gas oven for 30 minutes at 200 C, then 4.5 hours at 180 C. A number of potential microbiological critical control point failures were identified with the roast pork: the pork was home-killed and sold uninspected the pork was kept in a Northland marae chiller for 60 hours before being transported for 5 hours in chilly bins without ice packs from Kaitaia to Auckland, where it was then stored for a further 48 hours in a domestic refrigerator no temperature probe was used to ensure adequate cooking the cooked meat was cooled at room temperature for 1.5 hours before serving there was no system for sanitising utensils between use or separating cutting boards for raw and cooked foods. Discussion Despite this outbreak of foodborne illness causing significant morbidity among cases, the general practitioner consultation rate was low (6.3%). If this rate is representative of other outbreaks of self-limiting gastroenteritis, it remains a barrier to the adequate surveillance and investigation of foodborne illness. The isolation of a number of potential pathogens from the faeces of the three cases tested was unusual. The pattern of illness is most likely explained by infection with enterotoxin-producing C. perfringens. This organism, including its enterotoxin, was found in amounts >10 5 cfu/g in the faeces of all three cases tested. These levels are consistent with current infection or convalescence (Wong TL. Personal communication, 1996). The incubation period and relatively low incidence of vomiting are also consistent with C. perfringens food poisoning. 1 C. perfringens is a common contaminant of meat products. 2 Although C. perfringens was not isolated from the uncooked pork, the cooked pork leg served at the lunch remains the most likely source of infection, based on the results of the epidemiological investigation. The fact that C. perfringens was not isolated from the pork is not unexpected, as the vegetative cells of this organism are less viable after freezing. Therefore, any C. perfringens present on the meat would have existed mainly as spores, which are not detectable on routine testing. While coagulase-positive Staphylococci were found in the stool specimens of the three cases tested, staphylococcal intoxication was unlikely to be the cause of the illness in the majority of cases. Neither the incubation period, nor the low incidence of vomiting, 3 are typical of staphylococcal intoxication. The HACCP assessment identified several food handling practices that may have contributed to the contamination of the cooked pork: The meat was uninspected, which can result in greater potential for microbial contamination because the slaughter practices are not controlled. The faecal coliform count on the uncooked pork leg was higher than would be expected for fresh meat prepared under good manufacturing practice, and indicates that there was probably poor hygiene during Table 3: Results of microbiological analysis of faecal specimens from three cases of gastroenteritis following an Auckland hui Case number Organism/toxin identified 1 C. perfringens (> 2.0 x 10 6 cfu/g), C. perfringens enterotoxin, Coagulase-positive Staphylococci, 1 Campylobacter coli 2 C. perfringens (> 2.5 x 10 5 cfu/g), C. perfringens enterotoxin, Coagulase-positive Staphylococci, 1 Campylobacter jejuni 3 C. perfringens (> 1.6 x 10 6 cfu/g), C. perfringens enterotoxin, Coagulase-positive Staphylococci, 1 1 staphylococcal toxins not tested for The New Zealand Public Health Report Vol. 5 No. 5 May 1998 Page 34

slaughter or subsequent handling. The uncooked pork was transported unrefrigerated for a period of 5 hours. While the reported cooking times appear adequate, no temperature probe was used to ensure adequate cooking temperatures were reached, especially in the centre of the rolled loins. Rolled meats provide favourable growth conditions for C. perfringens as the organisms are transferred into the centre of the food, where heat penetration and cooling are slow and anaerobic conditions occur. Exposure of C. perfringens spores to temperatures of 75-80 C for 10-20 minutes can result in activation of the spores, which then grow immediately upon cooling. The cooked meat was left to cool at room temperature for 1.5 hours before serving. C. perfringens has a very short generation time: less than 10 minutes at its optimum temperature (43-47 C). Therefore, the organism could have multiplied many times before and during serving. The elevated risk associated with the eight other lunch foods, which could not be explained by confounding, suggests that these foods were contaminated by the pork during storage, preparation, or serving. The lack of sanitation of equipment between uses, especially between use for raw and cooked foods, probably contributed to cross contamination of other foods. Foodborne illness among participants at similar hui and other functions on marae has occurred (J Jarman. Personal communication, 1998), but the incidence is unknown. In 1997, outbreaks at hui were recorded (see the report on outbreaks in this issue s Surveillance and control notes). Notably, cases of food poisoning associated with traditional Maori foods are rarely reported. 4 Food safety programmes for the production of marae food, including traditional dishes cooked by hangi, should be straightforward. The promotion of food safety programmes in marae is recommended. Auckland Healthcare is commencing work with iwi throughout the greater Auckland region to promote food safety. Acknowledgments: Thanks are expressed for assisting with this investigation to the Auckland Healthcare health protection officers and sampling officers; Ray Wiblin, Health Protection Officer, Northland Health; and Maurice Wilson, Scientist, ESR. References 1 Shandera WX, Tacket CO, Blake PA. Food poisoning due to Clostridium perfringens in the United States. J Infect Dis 1983; 147: 167. 2 Lund BM. Foodborne disease due to Bacillus and Clostridium species. Lancet 1990; 336: 982-6. 3 Mandell GL, Douglas RG, Bennett JE, editors. Principles and practice of infectious diseases. 3rd ed. New York: Churchill Livingstone; 1990. 4 Gray M, Hasell S, O Reilly R, et al. Food Safety Assessment of Traditional Maori Foods. Christchurch: Te Runaka ki Otautahi o Kai Tahu; Institute of Environmental Science and Research; 1996. Surveillance and control notes Cryptosporidiosis outbreak in Lower Hutt associated with swimming in local pool There was a large increase in cases of cryptosporidiosis in March, with 60 cases notified nationwide (Figure 1). Twentythree of the 60 cases were from the Hutt Health District. Cryptosporidiosis is usually more common in the spring months, so an increase at this time of the year is unusual. However, as Figure 1 shows, there was a similar, although smaller, increase in cases in the Hutt Health District in April 1997. An outbreak investigation in Lower Hutt, including a casecontrol study and site investigations, provided good evidence linking this outbreak to a local public swimming pool. Cryptosporidium was found in the pool water. The pool was subsequently closed. There will be a full report on this outbreak in the next issue of the New Zealand Public Health Report. Control of cryptosporidiosis transmission in swimming pools presents a challenge. Prevention measures need to focus on minimising the risk of the pool water becoming contaminated. People with diarrhoea, or a history of diarrhoea in the previous 2 weeks, should not use pools. Pool users should be asked to shower thoroughly before going into the pool. Public health measures to prevent further such outbreaks should include the provision of specific information to pool owners and operators on how to minimise the risk of the water becoming contaminated. In addition, future pools should be designed to minimise the risk of transmission of infection. Cryptosporidiosis became a notifiable disease in June 1996. Medical practitioners can support control efforts and the rapid identification of outbreaks by promptly notifying cases. Cryptosporidiosis should be considered in the differential diagnosis of gastroenteritis, particularly if the symptoms persist for more than 3 days, and specific laboratory tests should be ordered. Medical practitioners should discuss with immunecompromised patients the risk and benefits of swimming, and advise such patients on precautions they may need to take. Cryptosporidiosis is potentially fatal for the immunecompromised, notably people with HIV/AIDS. Of the 652 AIDS notifications since 1984, eight (1.2%) had cryptosporidiosis as the AIDS-defining condition. This proportion probably under-estimates the impact of cryptosporidiosis in this group, as people with AIDS could be infected with cryptosporidiosis after the AIDS notification has been made. First influenza isolates of the 1998 season Three isolations of influenza virus were made in March; the first for the 1998 season. The patients were from Central Auckland (1), Waikato (1), and Canterbury (1) Health Districts. All isolates were Influenza A H3N2. Page 35 The New Zealand Public Health Report Vol. 5 No. 5 May 1998

Surveillance and control notes Impact of hepatitis B immunisation programmes A total of 136 cases of hepatitis B were notified in 1997 (Figure 2); a rate of 3.8 cases per 100 000. This rate is significantly higher than the 1996 rate of 3.0 per 100 000. Two cases died; a case-fatality rate of 1.5%. The majority (60.3%) of cases were male. Based on the risk factor information reported, 27.1% (13/48) of cases had sexual contact with a case or carrier, 14.8% (8/54) had household contact with a case, 13.5% (10/74) had travelled overseas, and 7.9% (5/63) had a history of injecting drug use. In addition, one case was a child born to a carrier mother, and one case was occupationally exposed to blood. ages probably reflects a lower uptake among this group. Older adults have not been routinely offered vaccination. While the incidence of hepatitis B decreased for all ethnicities between the two time periods, the largest percentage decrease was observed among Europeans (Figure 4). The impact of the hepatitis B immunisation programmes is evident from Figure 2, with the rate of the disease decreasing steadily since the introduction of these programmes, which began with the immunisation of certain high-risk groups in 1985 and culminated with the addition of hepatitis B immunisation to the childhood immunisation schedule in 1988. Figures 3 and 4 compare the rates of hepatitis B by age and ethnicity in the 5 years immediately succeeding the addition of hepatitis B immunisation to the schedule (1988-92) with the following 5 years (1993-97). Except for children under one year of age, the largest percentage decreases in the incidence of hepatitis B between the two time periods occurred in children 1-15 years of age (Figure 3). Hepatitis B is now relatively rare in children under 15 years, with only 34 cases notified in the 5- year period 1993-97. This larger impact in children under 15 years of age is expected, as children in this age range should have been offered vaccination either as infants or as part of the catch-up programme run at the time the vaccine was added to the schedule. Young adults, 16-22 years, should also have been offered vaccination, but the smaller decline in disease in these Measles case numbers now low throughout New Zealand Figure 5 shows that measles case numbers are now low in all areas of the country, following the epidemic last year. In March, there were just 23 cases (3 confirmed, 13 probable, and 7 other cases). These March cases bring the measles case notification total since 1 January 1997 to 2103, with 218 hospitalised cases but no deaths. A further 278 cases were laboratory-confirmed but not notified. Meningococcal disease alert as winter approaches The current rate of meningococcal disease rose again in March to 17.6 cases per 100 000. There were 26 cases notified in March. In the first 3 months of 1998 there were 47.4% more cases than in the same 3 months in 1997 (84 versus 57). Using an ARMA (autoregressive moving average) time-series model, and assuming that the rate of meningococcal disease will continue to increase, it is predicted that there will be approximately 800 cases of meningococcal disease in 1998 (a rate of 22 per 100 000). Table 1 shows meningococcal disease notifications and incidence rates by age group and ethnicity for 1997. The highest rates of disease were in those under one year of age. In all age groups, rates of disease in Pacific Islands people and Maori were higher than those in the European population. The highest rate of 876.1 cases per 100 000 was among Pacific Islands children under one year of age. The New Zealand Public Health Report Vol. 5 No. 5 May 1998 Page 36

Surveillance and control notes Table 1: Meningococcal disease notifications and incidence rates 1 by age group and ethnicity, 1997 Age group (years) European Maori Pacific Islands Other Unknown Total people ethnicity ethnicity No. Rate No. Rate No. Rate No. Rate No. No. Rate <1 24 76.5 42 282.9 41 876.1 5 167.3 3 115 210.2 1-4 36 26.9 86 151.3 78 427.0 11 96.8 7 218 96.9 5-9 21 12.1 25 37.1 30 144.3 2 14.0 4 82 28.5 10-14 20 12.3 21 36.7 11 64.0 5 31.2 2 59 22.3 15-19 34 20.9 11 21.3 4 23.8 4 20.0 2 55 20.9 20-29 22 6.0 6 6.6 3 9.5 3 9.9 1 35 6.4 30-39 11 2.7 3 3.8 3 11.2 2 5.6 0 19 3.3 40 17 1.5 4 3.8 5 13.5 4 9.0 1 31 2.2 Total cases and crude rate 185 7.1 198 37.8 175 101.1 36 20.5 20 614 17.0 Age-standardised rate 8.1 23.9 66.1 19.3 17.0 1 rate per 100 000 The higher total crude rates of meningococcal disease in Pacific Islands people (101.1 per 100 000) and Maori (37.8) than in Europeans (7.1) are partly due to the higher proportion of young people in the Pacific Islands and Maori populations. When these differences in age distribution are allowed for in age-standardised rates, the rate decreases in Pacific Islands people to 66.1 per 100 000 and in Maori to 23.9, while it increases to 8.1 in Europeans. During 1997, there were more cases of meningococcal disease in males (365, 59.4%) than in females (249, 40.6%). This gender distribution is similar to that seen in previous years. Given the rate of meningococcal disease predicted for 1998, and the fact that the majority of cases of meningococcal disease occur in the winter and spring months, medical practitioners should maintain a high level of suspicion for the disease over the next few months, particularly among Pacific Islands and Maori infants. Outbreaks of communicable diseases in 1997 There is now active surveillance of outbreaks of communicable diseases. Summary data on outbreaks are recorded on Episurv, the notifiable disease electronic database, in public health units. In 1997, 108 outbreaks of communicable diseases were reported to ESR. Twenty of the 24 health districts reported outbreaks during the year. The Auckland (three combined Auckland health districts) and Wellington Health Districts reported the largest number of outbreaks, 22 and 19 respectively. Giardia, Salmonella, small round structured viruses (SRSV), and Campylobacter were the most common causes of the outbreaks reported (Table 2). Two causative agents were identified or suspected in three outbreaks. Most outbreaks occurred within households (34 outbreaks, 31.5%), restaurants and cafes (23, 21.3%), hospitals and rest homes (14, 13.0%), or at special events or catered functions, including hui, (9, 8.3%). In the majority of recorded outbreaks, person-to-person contact (40 outbreaks) or food (37 outbreaks) was thought to be the probable mode of transmission of the pathogen or toxin. Some outbreaks had more than one probable mode of transmission. In 20 (65%) of the 37 foodborne outbreaks, one or more specific food items was implicated as the source of the outbreak. Chicken was the most common contaminated food, and was implicated or suspected in seven outbreaks. The most common factors probably contributing to the foodborne outbreaks were cross- contamination (9 outbreaks, 24.3%), inadequate hygiene of food handlers (9, 24.3%), and inadequate cooling or refrigeration of food (7, 18.9%). Medical practitioners can support the timely investigation and control of disease outbreaks by promptly reporting all cases of notifiable diseases to their medical officer of health. Urgent notification is particularly important where there is evidence of a common source of infection, for example, two or more linked cases of acute gastroenteritis. Table 2: Suspected causative agent of outbreaks reported during 1997 Suspected pathogen or toxin Number (percent) 1 of outbreaks Total number (percent) of cases Enteric infections (including food and waterborne diseases) Giardia 17 (15.7) 161 (10.3) Salmonella 14 (13.0) 152 (9.7) Small round structured virus 13 (12.0) 334 (21.4) Gastroenteritis (agent not specified) 13 (12.0) 134 (8.6) Campylobacter 12 (11.1) 145 (9.3) Hepatitis A 7 (6.5) 31 (2.0) Clostridium perfringens 5 (4.6) 146 (9.3) Staphylococcal toxin 4 (3.7) 12 (0.8) Viral gastroenteritis 3 (2.8) 55 (3.5) Bacillus enterotoxin 2 (1.9) 6 (0.4) Cryptosporidium 2 (1.9) 9 (0.6) Yersinia 2 (1.9) 5 (0.3) Bacillus subtilis 1 (0.9) 2 (0.1) Listeria monocytogenes 1 (0.9) 17 (1.1) Other infections (including airborne and person-to-person spread diseases) Measles 2 3 (2.8) 9 (0.6) Clostridium difficile 2 (1.9) 17 (1.1) Influenza A 2 (1.9) 226 (14.5) Neisseria meningitidis 2 (1.9) 4 (0.3) Extended spectrum ß-lactamase producing E.coli 1 (0.9) 14 (0.9) Haemophilus influenzae 1 (0.9) 58 (3.7) Legionella 1 (0.9) 3 (0.2) Mycobacterium tuberculosis 1 (0.9) 6 (0.4) Unknown 2 (1.9) 21 (1.3) Total 111 1564 Notes: 1 Percentage of the 108 outbreaks. Two pathogens or toxins were suspected in three outbreaks. 2 Includes only discrete outbreaks of measles. There was a widespread measles epidemic in 1997. Page 37 The New Zealand Public Health Report Vol. 5 No. 5 May 1998

Surveillance data National surveillance data - March 1998 Disease 1 Current year - 1998 2 Previous year - 1997 Trends - March 1998 Cumulative Cumulative Mar 1998 total this Current Mar 1997 total previous Previous cases year rate 4 cases year rate 3,4 AIDS Acute gastroenteritis 5 Campylobacteriosis Cholera Creutzfeldt-Jakob disease Cryptosporidiosis Dengue fever Giardiasis H. influenzae type b disease Hepatitis A Hepatitis B (acute) 6 Hepatitis C (acute) 6 Hydatid disease Influenza 7 Lead absorption Legionellosis 7 Leprosy Leptospirosis Listeriosis Malaria Measles Meningococcal disease Mumps Paratyphoid Pertussis 7 Rheumatic fever Rubella Salmonellosis Shigellosis Tetanus Tuberculosis Typhoid VTEC Yersiniosis 3 8 1.2 3 9 1.8 29 91 9.5 15 37 1104 2925 250.4 837 2797 233.1 0 0 0 0 0 0 0 0 0 0 1 60 91 11.4 19 37 3 7 0.6 1 2 0.4 262 630 59.0 234 623 1 2 0.3 2 5 0.8 14 48 8.3 32 94 7.3 5 17 3.4 8 32 3.0 8 34 2.8 10 23 1.9 0 0 0.1 0 0 0.1 3 3 17.9 1 3 18.6 6 15 2.0 8 17 12 50 4.2 6 15 1.5 0 0 0.1 0 0 0.2 9 23 1.7 6 13 1.4 3 8 0.8 8 15 0.6 12 26 2.1 9 16 2.5 23 74 56.9 24 55 26 84 17.6 19 57 13.2 15 25 2.5 6 25 0 1 0.6 0 6 0.7 0 4 0.7 4 23 8.1 2 8 2.1 6 32 3.5 11 20 1.9 11 34 312 732 41.7 142 400 30.6 10 33 3.3 8 27 3.9 0 1 0 0 0 0.1 23 82 9.3 25 77 9.8 4 10 0.6 1 4 0.4 3 9 0.5 1 2 0.2 65 208 15.6 42 131 Notes: 1 No cases of the following notifiable diseases were reported in March: anthrax, brucellosis, cysticercosis, diphtheria, meningoencephalitis - primary amoebic, plague, poliomyelitis, rabies, taeniasis, trichinosis, viral haemorrhagic fever, or yellow fever 2 These data are provisional 3 Historic data are incomplete for diseases that were made notifiable in June 1996 4 Rate is based on the cumulative total for the last or previous 12 months expressed as cases per 100 000 5 Cases with suspected common source, person in a high risk category (e.g. food handler, child care worker, health care worker) 6 Only acute cases of this disease are currently notifiable 7 Surveillance data based on laboratory-reported cases only 8 Percentage change is the difference between the number of cases in the current year (last 12 months) and the previous year (the 12 months up to and including March 1997). This difference is expressed as a percentage of the number of cases seen in the previous year. The New Zealand Public Health Report Vol. 5 No. 5 May 1998 Page 38

Surveillance data Surveillance data by health district - March 1998 Cases this month Current rate 1 Disease Cases for March 1998, 2 and current rate 1,2 by health district 3,4 North Health Midland Health Central Health Southern Regional Health AIDS 3 Acute gastroenteritis Campylobacteriosis Cholera Creutzfeldt-Jakob disease Cryptosporidiosis Dengue fever Giardiasis H. influenzae type b disease Hepatitis A Hepatitis B Hepatitis C Hydatids Influenza 5 Lead absorption Legionellosis 5 Leprosy Leptospirosis Listeriosis Malaria Measles Meningococcal disease Mumps Paratyphoid Pertussis 5 Rheumatic fever Rubella Salmonellosis Shigellosis Tetanus Tuberculosis Typhoid VTEC Yersiniosis Northland NW Auck Central Auck South Auck Waikato Tauranga Eastern BoP Gisborne Rotorua Taupo Taranaki Ruapehu 2 0 1 0 2.0 0.0 1.0 1.2 1 0 2 0 4 0 0 0 0 0 0 0 0 0 0 0 2 0 0 1 18 0 0 1 5.8 0.3 1.4 0 13.9 1.8 2.0 10.9 1.5 0 1.9 6.0 2.8 0 0 15.6 4.1 4.5 11.1 12.3 55.1 0 0 2.7 26 135 138 79 76 15 4 9 9 8 14 1 26 8 27 6 132 52 12 3 206 26 59 33 130.6 230.1 289.8 188.2 355.6 148.9 103.4 148.6 125.5 169.4 185.3 173.1 252.3 148.2 158.2 130.0 486.2 340.1 99.5 212.8 260.2 245.2 223.0 247.9 3 0 2 2 22 0 0 1 0 0 0 0 0 0 0 0 2 23 0 1 3 0 1 0 21.2 2.3 1.2 1.2 42.0 0.9 0 15.3 0 13.0 4.7 6.0 1.4 6.5 3.3 2.6 2.9 51.3 1.7 30.8 9.1 40.2 13.9 24.3 0 1 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.8 2.0 0.9 0.7 0 0 0 0 0 0 0 0 0 0 0 0.8 0 0 0 0 0 0.6 0 15 14 16 28 36 16 6 2 5 3 3 0 12 3 3 0 29 18 0 1 32 8 7 5 67.8 55.8 56.1 39.2 87.3 87.8 31.8 67.8 77.5 58.6 18.7 23.9 57.1 57.0 25.3 7.8 100.5 92.7 24.9 95.6 49.1 57.8 36.5 36.8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0.5 0.3 0.9 0 0.9 0 0 0 0 0 0 0 0 0 0 0 0.8 0 3.1 0 0 0 0 1 0 4 2 1 0 0 3 0 0 0 0 0 0 0 0 1 0 0 0 1 1 0 0 21.2 10.9 16.8 15.5 6.9 8.0 6.0 65.6 4.6 3.3 2.8 6.0 0.7 0 4.7 0 2.9 3.8 0 0 4.7 3.8 0.6 1.8 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 2.9 1.0 0.9 2.9 6.3 7.1 4.0 8.7 4.6 19.5 0.9 6.0 5.6 0 3.3 5.2 0.8 2.3 6.0 0 2.8 0 5.8 4.5 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 0 0 0 1.5 0.8 2.9 0.3 0 31.9 0 0 3.1 0 0.9 0 0.7 0 0.7 2.6 2.5 1.5 5.1 0 5.9 0 1.7 2.7 0 0.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.3 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 5.1 19.5 44.5 31.9 16.9 14.2 27.8 2.2 6.2 0 25.3 0 10.5 13.0 6.6 0 23.5 0.8 8.6 0 20.7 0 2.9 1.8 1 0 1 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 0.7 1.3 1.4 0.6 2.3 0 0 2.2 0 0 0 6.0 0.7 1.6 1.3 0 4.5 4.5 1.7 0 1.8 7.5 3.5 0.9 0 0 4 0 1 0 0 0 0 0 0 0 1 1 0 0 0 1 0 0 2 0 2 0 0.7 0.3 4.9 0.3 8.6 0 0 2.2 0 0 1.9 0 4.9 3.3 6.0 7.8 3.3 7.5 2.6 0 8.8 2.5 8.1 9.9 0 0 0.3 0.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 4 0 0 0 0 0 1 0 0 1 0 0 5.1 0.5 0 0 3.6 0 0 8.7 1.5 0 1.9 0 10.5 3.3 3.3 0 0 0 3.4 0 0.5 3.8 0.6 0.9 0 0 1 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0.7 0.5 2.3 1.2 0.7 0.9 2.0 0 0 0 0.9 0 1.4 0 0.7 0 0.4 0.8 0 0 0.8 0 0 0 0 2 2 0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 3 1 1 0 1.5 0.8 3.2 2.3 2.3 1.8 2.0 4.4 0 3.3 0 0 1.4 0.0 3.3 0 4.1 0 4.3 0 2.1 1.3 1.2 1.8 0 3 2 2 0 2 1 0 0 0 0 0 1 0 0 1 2 1 1 0 5 2 0 0 30.6 71.3 148.9 144.0 53.2 57.6 17.9 21.9 23.2 45.6 0.9 6.0 16.7 21.2 31.9 7.8 20.2 28.7 7.7 52.4 51.5 30.2 8.1 15.3 2 2 1 6 2 1 0 0 0 0 1 1 1 0 3 0 0 3 0 0 1 2 0 0 34.3 13.4 30.9 54.7 13.9 8.0 13.9 10.9 23.2 16.3 12.2 17.9 13.9 6.5 4.7 7.8 4.5 12.1 5.1 9.3 7.2 15.1 13.9 13.5 0 2 0 4 2 2 1 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 2 0 3.6 1.5 1.7 3.8 2.3 3.5 6.0 2.2 1.5 3.3 0 0 2.1 0 2.0 0 2.1 1.5 4.3 9.3 1.3 1.3 5.2 5.4 0 0.5 1.4 0.6 0.3 0 0 2.2 0 0 0 0 0 0 1.3 0 1.2 0 0 0 0.3 0 0 0 0 0 1.4 0 0.3 0 0 0 0 0 0.9 0 0 0 0 0 0.8 0 0 0 3.4 0 0 1.8 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7.3 0.5 2.0 6.1 2.0 2.7 0 13.1 0 0 1.9 0 2.8 0 0 0 2.1 0 0 0 0 0 0 2.7 0 1 1 0 0 3 0 0 1 0 0 0 1 0 0 0 2 0 0 0 0 0 2 0 0 1.3 1.4 1.8 1.7 3.5 2.0 0 1.5 0 0.9 6.0 5.6 0 0.7 0 2.1 0 3.4 0 1.0 0 6.4 2.7 3 28 16 22 29 6 7 2 3 0 8 1 6 2 6 5 13 13 18 1 79 16 23 5 28.4 40.1 54.1 46.8 44.0 34.6 39.8 19.7 17.0 26.1 31.8 11.9 27.2 22.8 19.9 52.0 44.9 38.5 47.2 86.3 65.4 80.5 39.4 46.7 1 0 2 2 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 5.1 4.6 7.8 7.3 3.3 0 2.0 0 1.5 0 0 0 2.1 0 0 2.6 0.4 6.0 0 0 3.4 2.5 0.6 2.7 0 0 0 0 0 0 2.0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 7 3 2 0 1 1 0 0 0 0 0 0 1 0 2 0 0 0 3 0 0 1 8.8 9.1 18.8 15.8 6.6 5.3 13.9 10.9 4.6 9.8 2.8 17.9 4.9 3.3 4.0 5.2 17.7 10.6 0.9 6.2 7.8 2.5 2.3 3.6 0 0 0 2 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 0 0.5 0.9 2.3 0 0 0 0 0 0 0 0 0.7 0 0 2.6 0.8 0 0.9 0 0 1.3 0.6 0 0 0 0 0 0 2 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.3 0.6 0.3 0.7 3.5 0 0 6.2 0 0 0 0 4.9 0 0 0 0 0 0 0.3 0 0 0 3 12 9 4 6 2 0 0 2 0 1 0 5 0 0 0 4 1 0 1 13 0 1 1 10.2 19.3 17.4 15.2 17.8 9.8 2.0 6.6 20.1 13.0 4.7 11.9 9.8 16.3 0.7 5.2 15.2 12.1 1.7 64.8 24.6 15.1 10.4 22.5 Hawkes Bay Wanganui Manawatu Wairarapa Wellington Hutt Nelson-Marl West Coast Canterbury South Cant Otago Southland Notes: 1 Current rate is based on the cumulative total for the last 12 months expressed as cases per 100 000 2 These data are provisional 3 AIDS data given by divisions of the Health Funding Authority 4 Further data are available from the local medical officer of health 5 Surveillance data based on laboratory-reported cases only Page 39 The New Zealand Public Health Report Vol. 5 No. 5 May 1998

Public health abstracts Infant feeding practice has an effect on child health A cohort study of 545 children (5-7 years old) related infant feeding with childhood health, in particular, respiratory illness, height, weight, body fat, and blood pressure. Demographic, clinical, and feeding data had been collected prospectively during the children s first 2 years of life. The probability of ever having suffered a respiratory illness was lower for children who received exclusive breastfeeding before 15 weeks of age than for those who received partial breastfeeding (infant milk supplements before 15 weeks) or exclusive bottle feeding: 17% compared with 31% and 32%, respectively. Solid feeding before 15 weeks was associated with increased probability of wheeze, increased percentage body fat, and increased weight. The probability of ever having asthma was not associated with infant feeding. Systolic blood pressure was higher among children who were bottle-fed as infants. (Wilson AC, Forsyth JS, Greene SA, et al. Relation of infant diet to childhood health: seven year follow up of cohort of children in Dundee infant study. BMJ 1998; 316: 21-5.) Editorial note: Many studies have shown the benefits of breastfeeding to both mother and baby during the first years of life. This study suggests that the benefits of breastfeeding may extend into early childhood. In New Zealand, rates of breastfeeding are high (80-90%) immediately after birth, but drop markedly during the first 6 months of life. In 1994, the Ministry of Health set the following objectives for breastfeeding in this country: to increase full breastfeeding at 3 months to 70% by 1997 and 75% by the year 2000, and to increase breastfeeding (full or partial) at 6 months to 70% by 1997 and 75% by the year 2000. In 1996, the prevalence of full breastfeeding at 3 months was 48% and the prevalence of full or partial breastfeeding at 6 months was 57%. Sexual activity may have a protective effect on men s health A cohort study of 918 men aged 45-59 years from Caerphilly in South Wales examined the relationship between orgasmic frequency and death. After ten years follow-up, mortality rates from all causes and from coronary heart disease were compared among three groups of differing orgasmic frequency. The all-cause mortality risk in the group with high orgasmic frequency was less than half that of the group with low orgasmic frequency (age-adjusted odds ratio [OR] 2.0; 95% confidence interval [CI] 1.1-3.5). The association between mortality and orgasmic frequency was strongest for mortality from coronary heart disease (age-adjusted OR 2.2; 95% CI 1.0-5.2). The authors concluded that, if their findings are replicated, intervention programmes promoting increased sexual activity could be considered. (Smith GD, Frankel S, Yarnell J. Travel health Sex and death: are they related? Findings from the Caerphilly cohort study. BMJ 1997; 315: 1641-5.) Editorial note: The results reported in this study should be treated with caution, as pointed out in a response to this paper (Hotopf M, Wessely S. The earth may move, but let s keep our feet on the ground. BMJ 1997; 315: 1645). While the study took some confounding factors, such as age, into account, other potentially confounding factors, such as depressed mood and vital exhaustion, were not considered. Hotopf and Wessely argue that these are risk factors for early death and predictors of reduced sexual activity. Reverse causation could also account for the observed association, that is, people suffering from symptoms of early heart disease may have reduced sexual activity. Japanese encephalitis expands its range to mainland Australia, Irian Jaya, and Nepal Australian health authorities reported, in March, the first case of Japanese encephalitis (JE) to be diagnosed in mainland Australia. The patient, who has now recovered and been discharged from hospital, is believed to have acquired the virus while working on a boat on the west coast of the Cape York Peninsula. The source is being investigated. This case follows the diagnosis of JE in the outer Torres Strait islands of Australia for the first time in 1995. (Australian National Centre for Disease Control website: http:/ /www.health.gov.au/pubs/cdi/cdihtml.htm.) The first proven outbreak of JE in the Kathmandu Valley in Nepal was also recently reported. This outbreak occurred in 1995 and resulted in 15 documented cases of meningoencephalitis. Many more cases went undetected. (Zimmerman MD, Scott RM, Vaughn DW, et al. Short report: an outbreak of Japanese encephalitis in Kathmandu, Nepal. Am J Trop Med Hyg 1997; 57: 283-4.) The first case of JE in Irian Jaya has recently been confirmed. Until this case, JE had not been reported east of Bali. (Spicer PE. Japanese encephalitis in western Irian Jaya. J Travel Med 1997; 4: 146-7.) Editorial note: These reports confirm the expanding range of JE. Since the disease was identified in Japan in the 1930s, it has spread through Korea, China, India, Southeast Asia, and Indonesia. The Kathmandu Valley in Nepal now needs to be added to the list of places where precautions against JE need to be taken. Vaccination can be considered for those expecting to spend more than a month in endemic areas. The New Zealand Public Health Report is produced monthly by ESR for the Ministry of Health. Internet website: http://www.moh.govt.nz/phg/phr.htm Scientific Editor: Michael Baker, Public Health Physician, ESR Managing Editor: Helen Heffernan, Scientist, ESR Editorial Committee: Sally Gilbert, Senior Advisor, Ministry of Health Michael Bates, Epidemiologist, ESR Louise Signal, Senior Advisor, Ministry of Health Phone: (04) 237 0149 Fax: (04) 237 2370 Phone: (04) 496 2000 Fax: (04) 496 2340 Reprinting: Articles in The New Zealand Public Health Report may be reprinted provided proper acknowledgement is made to the author and to The New Zealand Public Health Report as source. Contributions to this publication are invited, in the form of concise reports on surveillance, outbreak investigations, research activities, policy and practice updates, or brief review articles. Please send contributions to: Scientific Editor, The New Zealand Public Health Report, ESR, PO Box 50-348, Porirua, Wellington, New Zealand. Phone: (04) 237 0149; Fax: (04) 237 2370; Email: michael.baker@esr.cri.nz The content of this publication does not necessarily reflect the views and policies of ESR or the Ministry of Health. The New Zealand Public Health Report Vol. 5 No. 5 May 1998 Page 40