New Zealand Public Health Report

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1 New Zealand Public Health Report ISSN Volume 6 Number 4 April 1999 Improving the surveillance of mosquitoes with disease-vector potential in New Zealand Mark Hearnden,* Department of Public Health, Wellington School of Medicine; Chris Skelly, Ministry of Health; Henry Dowler, Ministry of Health; and Philip Weinstein, Department of Public Health, Wellington School of Medicine Since 1994, the surveillance of mosquitoes with disease-vector potential in New Zealand has relied on periodic surveys, with additional surveillance activities at air and seaports. Four exotic mosquito species, capable of transmitting several arboviral and other mosquito-borne diseases, are known to be established in New Zealand. The most recent species to become established was Aedes camptorhynchus, the southern salt-marsh mosquito, which was detected in the Napier area in December Another three exotic species have been intercepted at New Zealand seaports in recent years, but have not become established. The surveillance of exotic mosquitoes has been upgraded, and now actively targets regions according to their assessed risk for mosquito introduction and establishment. Assessment of risk is based primarily on the locations of air and seaports, and the volume of international passengers and goods that pass through the ports. It also takes into account the availability of a receptive population of human and animal hosts, and the suitability of the local environment, including climate. North Island port cities, especially in Auckland and Northland, are considered to be at greatest risk. It is proposed that future surveillance will be enhanced by modelling potential mosquito distributions. However, at present, much of the data needed for modelling are not available. There have been no known outbreaks of mosquito-borne diseases, such as diseases caused by arboviruses (arthropodborne viruses), malaria or filariasis, in New Zealand. 1,2 However, New Zealand could experience an outbreak of one of these disabling or life-threatening diseases. Exotic mosquito vectors are already present and, with international trade, there is a constant threat of further exotic species being introduced. Up until late 1998, the vector competence of the exotic mosquitoes that had become established in New Zealand was considered limited, and no studies have yet investigated any synergistic role these species may have in initiating or perpetuating epidemics in the presence of more efficient vector species. The spread of any mosquito-borne disease in New Zealand is likely to be aided by the fact that the human population is nonimmune and susceptible. This susceptibility is exacerbated in that the population knows little about mosquito-borne diseases or anti-mosquito measures to minimise the risks of infection. Moreover, a lack of experience with the diagnosis of mosquitoborne diseases among New Zealand general practitioners, coupled with the limited range and availability of rapid diagnostic *Correspondence: Dr Mark Hearnden, Department of Public Health, Wellington School of Medicine, University of Otago, Box 7343, Wellington South. whale@wnmeds.ac.nz services for these diseases, could result in a delay in the recognition of any outbreak that did occur. Such a delay could enable the disease to become widespread. The mosquito-borne diseases that potentially pose the greatest threat to New Zealand are the arboviral diseases Ross River virus disease, dengue fever, Barmah Forest virus disease and Japanese encephalitis. Yellow fever, malaria and Bancroftian filariasis also warrant consideration, but are thought to present a much lower level of risk to New Zealand. 3 The surveillance of mosquitoes is a component of the Ministry of Health s strategy to raise awareness of the public health risks associated with mosquitoes and to upgrade New Zealand s Contents Improving the surveillance of mosquitoes with disease-vector potential in New Zealand 25 Surveillance and control notes 28 Surveillance data 30 Public health abstracts 32 Travel health 32 Page 25 New Zealand Public Health Report Vol. 6 No. 4 April 1999

2 capacity to manage such risks. Other components of the strategy include training of designated officers, co-ordination with other sectors, the development of guideline materials, monitoring sector performance, and reporting to the Minister for Biosecurity. In addition, a national pest management strategy for exotic mosquitoes is being prepared. 4 This article summarises the results of mosquito surveillance in New Zealand. It also discusses the new risk-based approach to mosquito surveillance and introduces the role of modelling to predict the potential distribution of disease-vector mosquitoes. Mosquito surveillance methods New Zealand s first major survey of larval mosquito populations was conducted during the season, 5 and followed the interception of Aedes albopictus in used tyres imported into Auckland in In September 1994, the Ministry of Health adopted a 10 Year Plan to survey New Zealand s mosquito fauna. The plan provided for annual mosquito spot checks in one or more health districts each year, 7,8,9,10 and for a larger, co-ordinated national survey every 5 years. During these annual checks and national surveys, all potential larval habitats throughout the selected health districts (with the exception of subterranean sites) were sampled over the summer period. 5,11 In addition to the annual spot checks and national surveys, public health services were required to carry out mosquito surveillance and control at air and seaports. This included routine surveillance using traps for larval and, in some cases, adult mosquitoes, and checks on arriving cargo (eg, machinery or used cars from Japan) likely to contain the eggs or larvae of exotic mosquitoes of public health significance. Public health services were also responsible for identifying potential mosquito breeding sites and arranging for such sites to be eliminated or the subject of active, ongoing control measures. They also had some responsibilities to record the distribution and habitat preference of existing mosquito species in New Zealand. The 10 Year Plan of spot checks and surveys was terminated early, as it was no longer considered the most appropriate method to detect new species of exotic mosquitoes. The spot check in various North Island locations was the last of the scheduled surveys under the plan. 10 With the termination of this plan, mosquito surveillance was upgraded and standardised throughout New Zealand. Public health services surveillance programmes now actively target regions according to their assessed risk for the introduction and establishment of exotic mosquitoes. The greatest resources are committed to areas and times of highest risk. Risk assessment is based primarily on introduction pathways, such as the locations of air and seaports, and the volume of international passengers and goods that pass through the ports. It also takes into account the availability of a receptive population of human and animal hosts, and the suitability of the local environment, including climate. A minimal mosquito surveillance programme for low-risk seaports (eg, Timaru, Bluff and Dunedin) includes inspection of all first-port-of-call vessels, fumigation of all containers with tyres, and dockside surveillance using pre-positioned tyres as monitoring devices during months with an average temperature above 10ºC. In contrast, a programme for a high-risk area includes activities throughout the year, and involves surveillance at seaports, airports and other areas of perceived high receptivity. Surveillance activities are increased during the times of greatest risk, that is, during summer in New Zealand and during periods when vectors are most abundant around overseas ports (eg, spring and autumn for A camptorhynchus in Australia). 12 Results Four introduced mosquito species are known to have become established in New Zealand (Table 1). Three of these exotic species, A australis, A notoscriptus and Culex quinquefasciatus, have been present for many years. 13 A notoscriptus and C quinquefasciatus featured prominently in all of the surveys conducted between 1993 and the summer (Table 1). A notoscriptus was the most common exotic and consistently the second most frequently sampled species after the native C pervigilans. In December 1998, the local public health service received complaints from the public of unusual biting by mosquitoes in suburbs of Napier. Investigation revealed that the exotic A camptorhynchus, the southern salt-marsh mosquito from Australia, had become established in habitats around Hawkes Bay airport. 14 This species had become more abundant than the native C pervigilans as measured by the collection of larvae in the area during the summer (Table 1). This collection, unlike previous sampling programmes, was part of a delimiting survey and concentrated on areas most likely to contain salt-marsh mosquitoes. A subsequent investigation determined that, if left unchecked, this species was likely to spread from a reasonably restricted area around Napier to other parts of the North Island, particularly Auckland and Northland, and eventually to suitable habitats throughout New Zealand. 14 As well as its capacity for efficient transmission of Ross River virus, 15 the mosquito is a significant nuisance as Table 1: Relative prevalence of the four established exotic mosquito species in New Zealand, Relative prevalence of each mosquito species 1 Sampling period Areas sampled North Island North Island National 3 Waikato 3 Gisborne 3 Palmerston Napier & & Taranaki 3 North 3 & & Haumoana Canterbury Wanganui 3,4 Reference Mosquito species 5 Culex (Culex) pervigilans Bergroth Aedes (Finlaya) notoscriptus (Skuse) Culex (Culex) quinquefasciatus Say Aedes (Halaedes) australis (Erichson) 0.01 <0.01 Aedes (Ochlerotatus) camptorhynchus (Thomson) 1 Notes: 1 Relative prevalences are shown as a proportion of the most commonly occurring species for the survey. Sampling data was not included in the reports for the and surveys, so species are ranked in order of abundance where 1=most abundant. 2 Unpublished data from a delimiting survey initiated following complaints from the public about mosquitoes biting. 3 No subterranean habitats sampled. 4 Additional sampling at Wanganui found C pervigilans only, therefore proportions do not include data from Wanganui. 5 Exotic species are shown in bold type. New Zealand Public Health Report Vol. 6 No. 4 April 1999 Page 26

3 a day-biting species capable of interrupting outdoor activities. 16 In addition to these four exotic species that have become established, another three exotic species have been intercepted at New Zealand seaports in recent years, but do not appear to have become established (Table 2). A albopictus and A japonicus were found in used types imported into Auckland in These same two species were detected in and eradicated from used Japanese vehicles arriving in Auckland in January A albopictus was again detected in imported used Japanese vehicles in Wellington in August In March 1999, there were three further interceptions: A japonicus in Auckland, A albopictus in Tauranga, and C annulirostris in Napier. Discussion None of New Zealand s native or introduced mosquito species are known to have transmitted human arboviruses or other mosquito-borne diseases in this country, but their potential to do so remains to be fully investigated. 17 New Zealand has 12 native species of mosquito, of which C pervigilans is the most ubiquitous. 5 The four exotic mosquito species known to be established in New Zealand, and species which have been intercepted but have not become established, are competent vectors of several arboviral and other mosquitoborne diseases (Table 2). Ross River virus, which is prevalent throughout much of Australia, Papua New Guinea and the Solomon Islands, can be carried by almost all established, intercepted or potential exotic species listed in Table 2. The risk assessment approach to mosquito surveillance has identified port cities, particularly in Auckland and Northland, to be at greater risk than cities without major international air or seaports. 3 Auckland has been assessed to have the highest risk, based on the fact that it has the highest population density, the second highest population growth rate, and the highest annual temperature of any New Zealand city; its international air and seaports receive 75% of passenger arrivals in New Zealand, 74% of bulk shipping cargo, 35% of direct arrivals by overseas vessels (including yachts), and 50% of the imported retreaded or used pneumatic tyres; and there is a large movement of people between Auckland and the Pacific Islands. Northland is rated second in terms of risk for the introduction and establishment of exotic mosquitoes. Wellington and Christchurch are categorised as medium risk. However, lower annual average temperatures (and high wind in Wellington) would reduce the risk in these two cities compared with other medium-risk cities, such as Tauranga, Napier and Gisborne. Apart from Christchurch, it is difficult to rate other major South Island localities, mainly because low temperatures, especially in winter, reduce the likelihood of exotic mosquitoes becoming established. It is notable that under a risk-based methodology, Napier rates as only medium risk, due mainly to it having very little international air traffic and not being a first-port-of-call for international container ship traffic. Napier remained substantially unsurveyed during the annual spot-checks under the 10 Year Plan. The interceptions of A albopictus and A japonicus in Auckland in early 1998 prompted a review of inspection procedures at seaports in Napier, Wellington and Christchurch. However, habitats that were likely to harbour A camptorhynchus were still not inspected, as previous risk assessment had recommended focusing on freshwater container-breeders. 3 Anecdotal information received from the public during the Hawkes Bay eradication programme early in 1999, suggested that A camptorhynchus may have been present at least a year earlier. In New Zealand, changing climatic conditions resulting from El Ninõ Southern Oscillation (ENSO) events and global warming represent a new threat. Elevated temperatures and rainfall would lead to an increase in the number and extent of habitats that could support introduced insect vectors. A albopictus and C annulirostris, which have already been intercepted, represent a major threat. Both have a proven ability to colonise new habitats and act as efficient vectors for arboviral disease. A albopictus is a container-breeder and an important vector in the urban transmission of dengue virus. C annulirostris is one of Australia s most important arbovirus vectors. It is very similar to New Zealand s most abundant native species, C pervigilans, in that it breeds in a wide selection of standing freshwater habitats, but can also tolerate saline and mildly polluted waters. Other species common in the Pacific region, and which could potentially establish in New Zealand if the climate becomes wetter and warmer, are A aegypti, A vigilax (the northern saltmarsh mosquito from Australia), and A polynesiensis (Table 2). A aegypti is a container-breeder and the principal vector in the urban transmission of dengue virus throughout much of the world. 18 A polynesiensis has been responsible for epidemics of arboviral disease in Fiji, Samoa and the Cook Islands. 19 Table 2. Established, intercepted and potential exotic mosquito species of public health significance to New Zealand and their known or suspected vector competence for disease Current exotics (well-established in New Zealand) Disease 1 Ban BF Chik Den EEE JE Kun MVE RR VEE WEE YF Aedes (Halaedes) australis (Erichson) + Aedes (Ochlerotatus) camptorhynchus (Thomson) + + Aedes (Finlaya) notoscriptus (Skuse) + + Culex (Culex) quinquefasciatus Say Intercepted exotics (intercepted at least once, but never established) Aedes (Stegomyia) albopictus (Skuse) Aedes (Finlaya) japonicus (Theobald) + Culex (Culex) annulirostris Skuse Potential exotics (never found, but a potential threat with climate change) Aedes (Stegomyia) aegypti (L.) Aedes (Stegomyia) polynesiensis Marks Aedes (Ochlerotatus) vigilax (Skuse) Notes: 1 Ban, Bancroftian filariasis (Wuchereria bancrofti); BF, Barmah Forest virus disease; Chik, Chikungunya; Den, dengue fever; EEE, VEE, WEE, Eastern, Venezuelan and Western equine encephalitis; JE, Japanese encephalitis; Kun, Kunjin; MVE, Murray Valley encephalitis; RR, Ross River virus disease; YF, Yellow fever. Page 27 New Zealand Public Health Report Vol. 6 No. 4 April 1999

4 Assessment of the risks that New Zealand faces from exotic mosquito species could be enhanced by modelling potential mosquito distributions based on the mosquitoes physiological tolerances and physical requirements for colonisation. Ideally, models would incorporate the extremes and variability of climatic parameters (temperature, humidity and precipitation), and the distribution of physical habitat types and other factors likely to affect the suitability of a habitat for the establishment of a mosquito species, such as the known distributions of other mosquito species. At present, much of these data are either not available for New Zealand or in a form too coarse for accurate fine-scale resolution. The current challenge lies in developing models with available data and testing these to determine what is required to resolve small scale errors in prediction so that models become a useful predictive tool for public health intervention. As a final point, Dr Duane Gubler of the United States Centers for Disease Control and Prevention has noted that, along with efforts to reduce and reverse global warming, there should be a direction of resources toward public health measures to prevent the spread of disease, noting in particular that the most effective way to mitigate the effect of climate change is to rebuild our public health infrastructure and implement better disease-prevention strategies. 20 For the future, lessons learnt through events such as the establishment of A camptorhynchus in Napier could be incorporated into the development of a better understanding of the risks, including the development of modelling tools for the assessment, characterisation and control of disease. It is hoped that these tools will facilitate an enhanced understanding of the risks New Zealand faces, which will feed back into the risk-based decision-making process now being established within the public health community. New Zealand s changing attitude to surveillance and control, which includes adding tools to our surveillance systems that incorporate a greater understanding of the factors limiting vector distribution, are a significant step towards a better disease prevention strategy. References 1 Weinstein P, Laird M, Calder L. Australian arboviruses: at what risk New Zealand? Aust NZ J Med 1995; 25: Boyd AM, Weinstein P. Anopheles annulipes; an under-rated temperate climate malaria vector. NZ Entomol 1996; 19: Kay BH. Review of New Zealand s programme for exclusion and surveillance of exotic mosquitoes of public health significance. Brisbane: Queensland Institute of Medical Research; Draft national pest management strategy for exotic mosquitoes of public health significance. Linfield: Ministry of Agriculture and Forestry; Laird M. Background and findings of the New Zealand mosquito survey. NZ Entomol 1995; 18: Laird M, Calder L, Thornton RC, et al. Japanese Aedes albopictus among four mosquito species reaching New Zealand in used tyres. J Am Mosq Control Assoc 1994; 10: Browne G. Report to the Ministry of Health on the New Zealand mosquito check [Ministry of Health internal report]; Browne G. Report on the New Zealand mosquito survey in Waikato and Taranaki. Edited by Ministry of Health, Public Health Policy and Regulation Section. [Ministry of Health internal report]; Browne G. Report on the New Zealand mosquito survey in Gisborne. Edited by Ministry of Health, Public Health Policy and Regulation Section. [Ministry of Health internal report]; Report on mosquito surveys. Palmerston North spot check and other port surveys. [Ministry of Health draft internal report]; Laird M. New Zealand s northern mosquito survey, J A Mosq Control Assoc 1990; 6: Mackenzie JS, Lindsay MD, Coelen RJ, et al. Arboviruses causing human disease in the Australasian zoogeographic region. Arch Virol 1994; 136: Weinstein P, Laird M, Browne G. Exotic and endemic mosquitoes in New Zealand as potential arbovirus vectors. Wellington: Ministry of Health; Hearnden MN. A health risk assessment for the establishment of the exotic mosquitoes Aedes camptorhynchus and Culex australicus in Napier, New Zealand. Wellington: University of Otago; Ballard JWO, Marshall ID. An investigation of the potential of Aedes camptorhynchus (Thom.) as a vector of Ross River virus. Aust J Exp Biol Med Sci 1996; 64: Russell RC. Mosquitoes and mosquito-borne disease in southeastern Australia. 2nd ed. Sydney: University of Sydney; Kay BH, Hearnden MN, Oliveira NMM, et al. Alphavirus infection in mosquitoes at the Ross River reservoir, North Queensland, J Am Mosq Control Assoc 1996; 12: Knudsen AB. Global distribution and continuing spread of Aedes albopictus. Parasitologica 1995; 37: Marshall ID, Miles JAR. Ross River virus and epidemic polyarthritis. Curr Topics Vector Res 1984; 2: Taubes G. Apocalypse not. Science 1997; 278: Surveillance and control notes Decline in AIDS cases in 1998 but an increase in people living with HIV The incidence of AIDS continued to decline in 1998, with 29 cases notified (a rate of 0.8 per ), compared with 43 notifications in 1997 (Figure 1). A cumulative total of 669 cases of AIDS have been notified in New Zealand since surveillance began in In contrast to AIDS notifications, the number of people newly found to be infected with HIV increased in 1998 to 105, from a count of 63 in 1997 (Figure 1). A cumulative total of 1336 people have been diagnosed with HIV since The decrease in AIDS notifications over the last two years is considered to be due to the introduction of more effective combination antiretroviral treatments which are delaying the development of AIDS in HIV-infected people. The sharp rise in 1998 in the number of people newly found to be infected with HIV was due to an increase in the number of infected people coming to New Zealand from areas with a high prevalence. The decline in the rate at which HIV-infected people are developing and dying from AIDS and the increase in those diagnosed with HIV has resulted in a continuing increase in the number of people living with diagnosed HIV infection. It is estimated that, at the end of 1998, there were approximately 770 people (650 males and 120 females) living with diagnosed HIV in New Zealand. The actual number infected with HIV will be higher. Table 1 shows the most likely means of infection for people notified with AIDS and diagnosed as infected with HIV in 1998 and in total up until the end of Notably, nearly half (48.6%) of those people newly diagnosed with HIV in 1998 were heterosexually infected, as opposed to just 10.5% during the previous years. The majority of heterosexual infections (81.7% of those in men and 72.7% in women since 1996) have been acquired outside New Zealand. The ethnic distribution among New Zealand Public Health Report Vol. 6 No. 4 April 1999 Page 28

5 Surveillance and control notes the total 669 AIDS cases notified to the end of 1998 is: European, 80.3%; Maori, 10.8%; Pacific Islands people, 2.7%; other ethnicities, 5.2%; and unknown, 1.1%. While the introduction of combination therapy is having an impact on the number of HIV-infected people developing AIDS, resistance to these drugs is already emerging and widespread resistance could again lead to an increase in AIDS cases. Therefore, control of this disease must continue to focus on reducing the spread of the virus. (Reported by the AIDS Epidemiology Group, University of Otago.) Table 1: Exposure category of people notified with AIDS and people with diagnosed HIV infection AIDS HIV infection 1 12 months Total to 12 months Total to Exposure category Sex to to No. % No. % No. % No. % Homosexual contact Male Homosexual contact & IDU Male Heterosexual Male Female Injecting drug user (IDU) Male Female Blood product recipient Male Transfusion recipient Male Female Not stated Perinatal Male Female Awaiting information/ Male undetermined Female Not stated Other Male Female TOTAL Notes: 1 includes people who have developed AIDS 2 infected overseas Hospitalisations and fatalities from notifiable communicable diseases in 1998 The total number of deaths from notifiable communicable diseases decreased from 89 in 1997 to 54 in Meningococcal disease accounted for the largest number of deaths in 1998 and the highest calculated case-fatality rate (Table 2). The case-fatality rates presented in the table generally reflect acute mortality as, except for AIDS, only deaths among cases both notified and dying in 1998 are included. The 15 deaths recorded for AIDS are all the deaths from AIDS in 1998, and therefore include deaths among cases notified before Consequently, a case-fatality rate has not been calculated for AIDS. In 1998, there were no cases of Creutzfeldt-Jakob disease, which usually has a 100% casefatality rate, and no fatalities recorded among the 16 cases of listeriosis, which can have a case-fatality rate of up to 50%. There was a 45% decrease in the number of AIDS deaths in 1998: 15 deaths compared with 27 in 1997 (see discussion on AIDS in the Surveillance and control note above). There was also a notable (47%) decrease in reported deaths from tuberculosis (from 15 deaths in 1997 to 8 in 1998), and the case-fatality rate similarly decreased from 4.5% in 1997 to 2.2% in The number of deaths from meningococcal disease was similar to the number (24) in 1997, but the casefatality was higher at 5.2% compared with 3.9% in Communicable disease fatalities are relatively rare, and need to be accurately recorded. Funeral directors are legally required to notify the local medical officer of health of any deaths from infectious diseases. This requirement of funeral directors is in addition to the requirement for medical practitioners to report notifiable diseases. Other communicable diseases which are not notifiable, for example influenza, also cause significant numbers of fatalities. Table 2: Fatal cases of notifiable, communicable diseases, Disease Number of fatal cases Total number of cases Case-fatality rate(%) AIDS Campylobacteriosis Legionellosis Meningococcal disease Salmonellosis Tuberculosis VTEC/STEC infection Yersiniosis Total 54 Notes: 1 based on data recorded with the case notification Hospitalisations due to notifiable communicable diseases in 1998 are shown in Table 3. These data are likely to underestimate hospitalisations as the data are usually collected around the time the case is notified. Any subsequent deterioration and hospitalisation of cases may not be recorded. Meningococcal disease accounted for the largest number of hospitalisations, followed by campylobacteriosis, then tuberculosis and salmonellosis. Several communicable diseases have high rates of hospitalisation, often because of the need for intravenous antimicrobial therapy as well as other intensive care. Table 3: Hospitalised cases of notifiable, communicable diseases, Disease Number of hospitalised cases Number of cases for which Hospitalisation hospitalisation rate(%) status reported Acute gastroenteritis Brucellosis Campylobacteriosis Cholera Cryptosporidiosis Dengue fever Giardiasis H influenzae type b disease Hepatitis A Hepatitis B Hepatitis C Hydatid disease Lead absorption Legionellosis Leptospirosis Listeriosis Malaria Measles Meningococcal disease Paratyphoid Pertussis Poliomyelitis Rheumatic fever Salmonellosis Shigellosis Tetanus Tuberculosis Typhoid VTEC/STEC infection Yersiniosis Total 1635 Notes: 1 based on data recorded with the case notification 2 seven of the 11 cases reported to be not hospitalised, died 3 diagnosed as vaccine-associated, not wild-type Page 29 New Zealand Public Health Report Vol. 6 No. 4 April 1999

6 National surveillance data - February 1999 Surveillance data Disease 1 Current year Previous year Trends - February 1999 Cumulative Cumulative Feb 1999 total this Current Feb 1998 total previous Previous cases year rate 3 cases year rate 3 AIDS Acute gastroenteritis 4 Campylobacteriosis Cholera Creutzfeldt-Jakob disease Cryptosporidiosis Dengue fever Giardiasis H influenzae type b disease Hepatitis A Hepatitis B (acute) 5 Hepatitis C (acute) 5 Hydatid disease Influenza 6 Lead absorption Legionellosis 6 Leprosy Leptospirosis Listeriosis Malaria Measles Meningococcal disease Mumps Paratyphoid Pertussis Rheumatic fever Rubella Salmonellosis Shigellosis Tetanus Tuberculosis Typhoid VTEC/STEC infection Yersiniosis Notes: 1 No cases of the following notifiable diseases were reported in February: anthrax, brucellosis, cysticercosis, diphtheria, meningoencephalitis - primary amoebic, plague, poliomyelitis, rabies, rickettsial diseases, trichinosis, viral haemorrhagic fever, or yellow fever 2 These data are provisional 3 Rate is based on the cumulative total for the last or previous 12 months expressed as cases per Cases with suspected common source, person in a high risk category (eg, foodhandler, childcare worker, healthcare worker) 5 Only acute cases of this disease are currently notifiable 6 Surveillance data based on laboratory-reported cases only 7 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 February 1998). This difference is expressed as a percentage of the number of cases seen in the previous year. New Zealand Public Health Report Vol. 6 No. 4 April 1999 Page 30

7 Surveillance data Surveillance data by health district - February 1999 Cases this month Current rate 1 Disease Cases for February 1999, 2 and current rate 1,2 by health district 3,4 Northern Midland Central Southern 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 Rheumatic fever Rubella Salmonellosis Shigellosis Tetanus Tuberculosis Typhoid VTEC/STEC infection Yersiniosis Northland NW Auck Central Auck South Auck Waikato Tauranga Eastern BoP Gisborne Rotorua Taupo Taranaki Ruapehu 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 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 31 New Zealand Public Health Report Vol. 6 No. 4 April 1999

8 Public health abstracts Smoking cessation interventions are a function for all healthcare Recently published smoking cessation guidelines for health professionals throughout the National Health Service in England recommend the integration of smoking cessation interventions into all routine healthcare. They are the first professionally endorsed, evidence- and consensus-based guidelines on smoking cessation for the English healthcare system. Assessment of the smoking status of patients at every opportunity, advising and assisting smokers to stop, and arranging follow-up are key recommendations of the guidelines. Brief (3 minutes) advice from a general practitioner is effective and has been shown to achieve a 2% increase in the proportion of smokers quitting for 6 months. The use of nicotine replacement therapy and/or the provision of intensive support further increases cessation rates. Many smokers will need more intensive help to stop. These smokers should be referred to specialist cessation services, which are usually group-based and have the added advantage of providing social support. The guidelines include additional recommendations for specific populations such as smokers at the point of hospital admission, pregnant smokers, and young smokers (Smoking cessation: evidence based recommendations for the healthcare system. BMJ 1999; 318: 182-5). Editorial note: Smoking cessation interventions are extremely cost effective. The Health Funding Authority has recently developed a broad strategy for smoking cessation, which identifies interventions that are most likely to succeed in New Zealand. Guidelines for smoking cessation in New Zealand are currently being developed and are due for release in July Like the English recommendations, the guidelines will include recommendations for all health professionals, but will target the primary healthcare setting. They will include specific advice for particular groups, such as Maori, teenagers and pregnant women. Recommendations for the use of antiretroviral drugs during pregnancy The latest advice from the United States Public Health Service on the use of antiretroviral drugs in HIV-infected pregnant women includes recommendations on the treatment of the woman s HIV infection during her pregnancy and updated recommendations on the use of zidovudine (ZDV) chemoprophylaxis to minimise perinatal transmission of HIV. Standard combination antiretroviral therapies to treat HIV infection should be discussed and made available to pregnant women. Pregnancy may affect decisions about timing and choice of therapy. Discussions should include the potential for adverse effects on the fetus. The safety of many antiretroviral drugs for the fetus has not yet been established. In addition to the standard antiretroviral therapy to treat the woman s infection, ZDV chemoprophylaxis should be incorporated into the treatment regime to prevent perinatal transmission of HIV. The three-part (ante-, intra-, and postpartum) Travel health ZDV regime, known as the PACTG Protocol 076, has been shown to reduce perinatal HIV transmission by approximately 70%. It is also effective in women with advanced disease, low CD4+ T-lymphocyte counts, and prior ZDV therapy (Public Health Service task force recommendations for the use of antiretroviral drugs in pregnant women infected with HIV-1 for maternal health and for reducing perinatal HIV-1 transmission in the United States. MMWR 1998; 47 (RR-2): 1-30). Editorial note: In New Zealand, the PACTG ZDV regime provides guidance for chemoprophylaxis to prevent perinatal HIV transmission. However, treatment is adjusted according to each woman s history. In 1998, four pregnancies among women known to be infected with HIV were reported to the New Zealand Paediatric Surveillance Unit. The actual number of HIV-infected pregnant women was likely to be greater, as HIV testing is not universal. ZDV chemoprophylaxis was offered to all four women, but was refused by one. Three of the pregnancies, including the one for which ZDV was refused, ended in live births. To date, none of the babies has been diagnosed with HIV infection. Nipah virus outbreak in Malaysia linked to direct contact with pigs An outbreak of febrile encephalitis occurred in Malaysia from September 1998 to April During this time, 229 cases were reported, of which 111 (48%) were fatal. A further 11 cases have occurred in Singapore. The illness was characterized by 3-14 days of fever and headache, followed by drowsiness and disorientation that could swiftly progress to coma and death. The causative agent is a newly identified paramyxovirus, which has been named Nipah virus. This virus is similar to the Hendra virus (originally called equine morbillivirus), which caused fatal human illness following contact with horses in Queensland in The primary source of Nipah virus in Malaysia appears to be pigs. Most of the cases have been pig farmers, and close contact with pigs appears to be necessary for human infection. There is no evidence of human to human transmission (Update: outbreak of Nipah virus Malaysia and Singapore, MMWR 1999; 48: 335-7). Editorial note: No restrictions on travel to Malaysia are recommended as a result of this outbreak. New Zealand Public Health Report is produced monthly by ESR for the Ministry of Health. Internet website: 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 Phone: (04) Fax: (04) Phone: (04) Fax: (04) 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, New Zealand Public Health Report, ESR, PO Box , Porirua, Wellington, New Zealand. Phone: (04) ; Fax: (04) ; 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. New Zealand Public Health Report Vol. 6 No. 4 April 1999 Page 32