The 1993 dengue 2 epidemic in North Queensland: a serosurvey and comparison of hemagglutination inhibition with an ELISA.

An epidemic of dengue type 2 infection occurred in North Queensland during 1992 and 1993. A random serosurvey of 1,000 residents of a population that experienced this epidemic only during 1993 was conducted to determine the proportion of the population at risk for secondary infection in the event of another epidemic with a different serotype. The ability of an ELISA to detect prior exposure to the dengue virus was compared with the hemagglutination inhibition assay. Dengue 2 virus plaque-reduction neutralization assays were performed to evaluate the specificity of the antibody response. Antibodies to dengue virus, or closely related flaviviruses, were detected in 61.9%. Seroprevalence increased with age and correlated well with known previous epidemics in the region. The sensitivity and specificity of the ELISA was 99.2% and 96.2%, respectively. An estimated 26% of the population was infected during the 1993 epidemic.

Body site specific incidence of basal and squamous cell carcinoma in an exposed population, Townsville, Australia.

Most data on body site distribution of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) do not take into account the surface proportion occupied by body sites experiencing differing amounts of ultraviolet radiation. The recording of BCC and SCC is heterogenous and body sites are not standardized. This study was undertaken to assess the magnitude of the incidence rates of skin cancers at different body sites in a population which experiences high ultraviolet exposure and involved all primary care services in Townsville over 6 weeks in June 1993. The annual site-specific age-standardized (World Population) incidence rates of histologically diagnosed lesions, determined from data where lesions were recorded on a body map, were adjusted for surface area and expressed per 100,000 body units (BU). Relative site densities of lesions were also calculated. Annual incidence rates for BCC per 100,000 BU on the most exposed face (ears, nose and cheeks) were 25,893 (95% confidence interval (c.i.) 18,837-32,950), 13,222 (95% c.i., 8273-18,171) on the less exposed face (forehead,eyebrow, chin and jaw) and 27,837 (95% c.i., 12,560-43,115) on the least exposed face (area within the orbit and nasolabial fold). Incidence rates for SCC rates were highest on the less exposed face, 5843 (95% c.i., 2627-9058) most exposed face, 4200 (95% c.i., 1274-7126) and the exposed upper limb, 3786 (95% c.i., 2783-4789). The relative site density of histologically confirmed BCC was 14 on the most exposed face in males compared with 5 in females and 11 around the eyes (least exposed) in males and 9 in females compared with the body as a whole. Adjustment for body surface proportion demonstrates that highly exposed body sites are at very high risk. The magnitude of the incidence rates on these sites is attributed to the combination of a susceptible population and high ambient ultraviolet radiation (UVR).

Augmentation of Pap smear screening of high risk aboriginal women. Use of a computerised process tool within the Broome Aboriginal Medical Service.

OBJECTIVE: The Broome Regional Aboriginal Medical Service (BRAMS) in Broome, Western Australia, conducted a 4 month program to augment the Pap smear screening of Aboriginal women. The emphasis was on those with a past history of abnormal smears, aged greater than 40 years, living in remote communities and very (more than 5 years) overdue. METHOD: Continuation of existing opportunistic recall processes supplemented by three components: the development of an Aboriginal Health Worker (AHW) run Pap smear clinic; the provision of Aboriginal outstation screening; and active recruitment of targeted women (by AHW staff) using worklists. All components used Healthplanner, a computerised process tool to facilitate targeting and recall. MAIN OUTCOME MEASURES: The number of Pap smears taken from the target groups before and after intervention and the proportion screened from the women eligible in each target group at the start of the program. RESULTS: There was statistically significant increase in the coverage of Aboriginal women overall, those over the age of 40 years, and those from remote communities when compared with the same period the previous years. In 4 months, 21-30% of Aboriginal women eligible for Pap smears in these high risk categories including those with past abnormal smears were screened. Over-screening of women did not occur as only 4% of smears taken were from women screened less than 12 months previously. Smears taken by AHW staff were of high quality. CONCLUSION: Use of a computerised process tool in a remote setting can facilitate selective recruitment of high risk women overdue for Pap smears.

Sun exposure and melanocytic naevi in young Australian children.

Queensland, Australia, has the highest rates of melanoma in the world and Queensland children have the greatest numbers of melanocytic naevi, the strongest risk factor for melanoma. Although both melanoma and naevi are broadly related to sun exposure in childhood, the relation to individual exposure early in life is difficult to study retrospectively in adults. We surveyed 506 children aged 1-6 years who had been born in Townsville, North Queensland. Sun exposure was assessed by questionnaire and melanocytic naevi were counted using a standard international protocol. Very high counts (upper quarter) of melanocytic naevi were significantly associated with sun exposure of more than 4 hours per day (adjusted relative risk ratio 3.29; 95% Cl 1.12-9.69), and with a history of sunburn (1.89; 1.11-3.21). Melanocytic naevus counts increased with age, light skin reflectance, and freckling. With exposure to intense ultraviolet light in Townsville, children develop melanocytic naevi early in life and in large numbers. We found that both acute and chronic exposure to sun are associated with their development.

Determinants of dengue 2 infection among residents of Charters Towers, Queensland, Australia.

Dengue fever is caused by one of the four serotypes of the dengue virus and is transmitted by the urban mosquito Aedes aegypti. In 1993, the city of Charters Towers in the tropical north of Australia experienced an epidemic caused by the dengue 2 virus. A cross-sectional sample of 1,000 people was assessed for determinants of recent symptomatic dengue infection. After exclusion of people with prior exposure to dengue 2, a study group of 797 persons, including 196 patients with recent infection, were evaluated. Stepwise logistic regression analysis identified four determinants of infection: the presence of a case of dengue fever within two residential blocks (odds ratio (OR) = 3.61, 95% confidence interval (CI) 2.56-5.10), house screening (OR = 0.60, 95% CI 0.40-0.89), the presence of a water tank within two residential blocks (OR = 1.51, 95% CI 1.02-2.22), and the use of knockdown insecticide (OR = 1.75, 95% CI 1.22-2.51). Classification and Regression Tree analysis identified a group of 152 individuals in whom the prevalence of dengue infection was 50%. These people lived within two blocks of a suspected dengue fever case, did not have house screening, and used knockdown sprays. If dengue had not occurred within two residential blocks, there were no additional factors that significantly influenced the prevalence of dengue fever. Control of dengue epidemics should involve attempts to geographically contain the spread of infection, use of house screening, and the removal of mosquito breeding sites such as water tanks.

The 1993 dengue 2 epidemic in Charters Towers, North Queensland: clinical features and public health impact.

In 1993 an epidemic caused by dengue virus type 2 occurred in several North Queensland population centres. Charters Towers, estimated population 10,000, had 155 officially notified cases. An analysis of symptoms was undertaken using a random sample of 1000 residents to determine specificity of symptoms, the subclinical infection rate, and to establish the true extent of the epidemic. Retrospective diagnoses of dengue fever were based on the presence of both serum dengue 2 neutralizing antibody and presence of symptoms. An estimated 20% of the population had dengue fever. The rate of subclinical infections in this epidemic was 14.6%. There were no symptoms that were specific for dengue fever. Bleeding occurred more frequently in people who recalled a previous dengue infection during a dengue 1 epidemic 12 years earlier (55.6% vs. 16.8%, P = 0.003). Surveillance for future epidemics should be based on serological and virological confirmation of dengue virus infection amongst symptomatic patient.

Excessive rates of childhood mortality in the Northern Territory, 1985-94.

OBJECTIVES: To estimate the post-infant/childhood mortality rate (1-14 years) in the Northern Territory (NT) of Australia. METHODS: A retrospective study of post-infant death in the 10 years 1985-94 inclusive in the NT. RESULTS: Two hundred and forty-four deaths were identified. Compared to a non-Aboriginal, an Aboriginal child was twice as likely to die from accidents, 11 times more likely to die from infection and 3.2 times more likely to die from all causes. Road traffic accidents were the leading cause of accident mortality in Aboriginal children. All children who died in collisions or rollovers were unrestrained. Drowning was the major cause of death amongst non-Aboriginal children aged 1-4 years; none of the residential pools in which drowning occurred had fencing which complied with the recommended Australian fencing standards. Mortality rates from infection were highest in Aboriginal children aged 1-4 years. The overall mortality rate decreased over the 10-year period with a significant reduction in non-Aboriginal but not in Aboriginal children. CONCLUSIONS: NT children aged 1-14 years have higher mortality rates than their Australian counterparts and these are significantly higher in Aboriginal compared to non-Aboriginal children. Legislation and enforcement of isolation pool fencing, car seat restraints and safer driving on rural roads could have a significant impact on reducing accident mortality.