Understanding SARS-CoV-2 Delta and Omicron variant transmission and vaccine impact in schools and child-care settings in Australia: a population-based study.

Background: Over 214 million students globally have been affected by school closures during the COVID-19 pandemic. To address knowledge gaps on transmission of SARS-CoV-2 delta (B.1.617.2) and omicron (B.1.1.529) variants in educational settings we examined virus transmission in schools and early childhood education and care settings (ECECs) in New South Wales (NSW), Australia in relation to mitigation measures, including COVID-19 vaccination. Methods: Secondary transmission from children and adults with laboratory-confirmed SARS-CoV-2 infection who attended a school (n = 3170) or ECECs (n = 5800) while infectious was investigated over two periods: 1) June 16 to September 18, 2021 (delta outbreak), and; 2) October 18 to December 18, 2021 (delta and omicron; schools only). Close contacts of cases underwent 14 days quarantine and SARS-CoV-2 nucleic acid testing. Secondary attack rates (SARs) were calculated and compared with state-wide notification data, school attendance, and vaccination status. Findings: 1187 schools and 300 ECECs had students (n = 1349) or staff (n = 440) attend while infectious. Of 24,277 contacts investigated, most (91.8%; 22,297/24,277) were tested and 912 secondary cases identified. The secondary attack rate (SAR) was 5.9% in 139 ECECs and 3.5% in 312 schools. The risk of becoming a secondary case was higher in unvaccinated school staff (OR 4.7; 95% CI: 1.7-13.3), particularly ECEC staff (OR 9.0; 95% CI: 3.6-22.7) and unvaccinated school students than in vaccinated school staff. SARs were similar for delta (4.9%) and omicron BA.1 (4.1%) in the unvaccinated and higher compared with vaccinated contacts (0.9% and 3.4%, respectively). Increasing school attendance rates raised case incursions and secondary case numbers, but not community-wide infection rates. Interpretation: Vaccination reduced SARS-CoV-2 transmission rates in schools, although less so for omicron than delta variants. Despite higher community-based transmission rates, in-school transmission remained low and stable with high attendance, suggesting that community restrictions, rather than school closures, best mitigated COVID-19 impacts. Funding: NSW Government Department of Health.

Q fever seroprevalence in Australia suggests one in twenty people have been exposed.

Q fever (caused by Coxiella burnetii) is thought to have an almost world-wide distribution, but few countries have conducted national serosurveys. We measured Q fever seroprevalence using residual sera from diagnostic laboratories across Australia. Individuals aged 1-79 years in 2012-2013 were sampled to be proportional to the population distribution by region, distance from metropolitan areas and gender. A 1/50 serum dilution was tested for the Phase II IgG antibody against C. burnetii by indirect immunofluorescence. We calculated crude seroprevalence estimates by age group and gender, as well as age standardised national and metropolitan/non-metropolitan seroprevalence estimates. Of 2785 sera, 99 tested positive. Age standardised seroprevalence was 5.6% (95% confidence interval (CI 4.5%-6.8%), and similar in metropolitan (5.5%; 95% CI 4.1%-6.9%) and non-metropolitan regions (6.0%; 95%CI 4.0%-8.0%). More males were seropositive (6.9%; 95% CI 5.2%-8.6%) than females (4.2%; 95% CI 2.9%-5.5%) with peak seroprevalence at 50-59 years (9.2%; 95% CI 5.2%-13.3%). Q fever seroprevalence for Australia was higher than expected (especially in metropolitan regions) and higher than estimates from the Netherlands (2.4%; pre-outbreak) and US (3.1%), but lower than for Northern Ireland (12.8%). Robust country-specific seroprevalence estimates, with detailed exposure data, are required to better understand who is at risk and the need for preventive measures.

Epidemiology and whole genome sequencing of an ongoing point-source Salmonella Agona outbreak associated with sushi consumption in western Sydney, Australia 2015.

During May 2015, an increase in Salmonella Agona cases was reported from western Sydney, Australia. We examine the public health actions used to investigate and control this increase. A descriptive case-series investigation was conducted. Six outbreak cases were identified; all had consumed cooked tuna sushi rolls purchased within a western Sydney shopping complex. Onset of illness for outbreak cases occurred between 7 April and 24 May 2015. Salmonella was isolated from food samples collected from the implicated premise and a prohibition order issued. No further cases were identified following this action. Whole genome sequence (WGS) analysis was performed on isolates recovered during this investigation, with additional S. Agona isolates from sporadic-clinical cases and routine food sampling in New South Wales, January to July 2015. Clinical isolates of outbreak cases were indistinguishable from food isolates collected from the implicated sushi outlet. Five additional clinical isolates not originally considered to be linked to the outbreak were genomically similar to outbreak isolates, indicating the point-source contamination may have started before routine surveillance identified an increase. This investigation demonstrated the value of genomics-guided public health action, where near real-time WGS enhanced the resolution of the epidemiological investigation.

Pregnant women's intention to take up a post-partum pertussis vaccine, and their willingness to take up the vaccine while pregnant: a cross sectional survey.

INTRODUCTION: Post-partum vaccination of new mothers is currently recommended in Australia to reduce pertussis infection in infants. Internationally, vaccination recommendations now include pregnant women in some countries. Understanding the awareness of pertussis vaccination recommendations among pregnant women, and their willingness to have the vaccine while pregnant is important for informing vaccine program implementation. OBJECTIVE: To determine awareness and intentions toward current recommendations for post-partum pertussis vaccination among Australian pregnant women, and their willingness to accept pertussis vaccine during pregnancy, should it be recommended in Australia in the future. DESIGN: Quantitative self-administered survey, using a non-random stratified sampling plan based on representative proportions by age, parity and region of residence. PARTICIPANTS AND SETTING: Pregnant women receiving antenatal care through three large, demographically diverse referral hospitals in metropolitan, urban and rural New South Wales, Australia. RESULTS: The response rate was 815/939 (87%). Most women (80%) reported willingness to have the pertussis vaccine during pregnancy, should it be recommended. Thirty four per cent of women intended to receive a pertussis vaccine post-partum, 17% had received it previously, while 45% had never heard of pertussis vaccine, had not thought about it, or were undecided about having it. Compared with those who had not received a recommendation to have the vaccine post-partum, women who had received a recommendation were 7 times more likely (95% CI 4-14) to report intention to have the vaccine. CONCLUSIONS: Health care provider recommendation is paramount to raising awareness of pertussis vaccination recommendations among pregnant women. Women's willingness to have the vaccine while pregnant is encouraging, and indicates the potential for high pertussis vaccine coverage among pregnant women, should it be recommended in Australia.

The utility of seroepidemiology for tracking trends in pertussis infection.

Comparing pertussis epidemiology over time and between countries is confounded by differences in diagnostic and notification practices. Standardized serological methods applied to population-based samples enhance comparability. Population prevalence of different levels of pertussis toxin IgG (PT IgG) antibody, measured by standardized methods, were compared by age group and region of Australia between 1997/1998 and 2002. The proportion of 5- to 9-year-olds with presumptive recent pertussis infection (based on IgG levels >or=62.5 ELISA units/ml) significantly decreased in 2002, consistent with notification data for the same period and improved uptake of booster vaccines following the schedule change from whole-cell to acellular vaccine. In contrast, recent presumptive infection significantly increased in adults aged 35-49 years. Population-based serosurveillance using standardized PT IgG antibody assays has the potential to aid interpretation of trends in pertussis incidence in relation to vaccine programmes and between countries.

Analysis of Barmah Forest virus disease activity in Queensland, Australia, 1993-2003: identification of a large, isolated outbreak of disease.

Barmah Forest virus (BFV) disease is the second most common mosquito-borne disease in Australia. Although the majority of notifications are received from Queensland, little is known about the distribution of the disease within the state, or the important mosquito vectors and nonhuman vertebrate hosts. We conducted a retrospective statistical analysis of the notifications received from Queensland residents from 1993 to 2003 to establish long-term local incidence rates and to identify disease outbreaks. In total, 4,544 notifications were received over the 10-yr period. Disease reporting peaked in autumn, although the peak transmission season encompassed both summer and autumn. Long-term standardized incidence rates for summer/autumn and winter/spring varied across the state, showing positive spatial autocorrelation in both 6-mo periods. Although 15 instances of increased disease activity were identified, only one major disease outbreak affecting eight contiguous local government areas was detected in summer/autumn 2002/2003. This outbreak contained 297 cases, 115 more than would be expected over this period. The factors important to this outbreak are unknown and require further investigation. Although the incidence rates for BFV disease are lower than Ross River virus disease, the most reported mosquito-borne disease in Australia, several factors indicate that this virus should be considered an important public health risk in Queensland. These include consistent endemic transmission, apparent underreporting of the disease, and the potential for outbreaks in major population centers.

The cell-mediated immune response to Neospora caninum during pregnancy in the mouse is associated with a bias towards production of interleukin-4.

Neospora caninum is an obligate intracellular protozoan parasite which is efficiently transmitted transplacentally in cattle where it may cause abortion. A pregnant mouse model was used to characterise the immune response following N. caninum infection; the response in non-pregnant and pregnant mice was compared. Spleen cells from both infected/non-pregnant and infected/pregnant mice produced interferon-gamma, interleukin-12 and tumour necrosis factor alpha; however, the levels of these Th1 cytokines were lower in infected/pregnant mice. Infected/non-pregnant and infected/pregnant mice also produced the Th2 cytokine interleukin-10; however, there was no trend toward a decrease of this in pregnant mice. Interleukin-4 was exclusively produced at high levels by infected/pregnant mice and thus appears responsible for the observed decline in Th1 cytokine production in pregnant mice. A bias towards Th2 cytokines such as IL-4 and IL-10 is normally associated with the maintenance of a viable pregnancy, and not with the control of protozoal infections. Consequently, the importance and role of cytokines and cell-mediated immunity in the control of transplacental transmission and foetal loss due to N. caninum infection are discussed.

Characterisation of the first Australian isolate of Neospora caninum from cattle.

OBJECTIVE: To isolate Neospora caninum from a congenitally infected calf. PROCEDURE: A calf was obtained from a N. caninum infected dam maintained in a dairy herd of Holstein-Friesian cattle located on the south coast of NSW near Nowra. The calf was euthanased and samples collected for serology and pathology. Samples of brain and spinal cord of the calf were homogenised and injected into immunocompromised mice in an attempt to recover protozoa by in vivo culture. Sequential passage of brain homogenate through IFNgammaPKO mice was performed and tissue culture flasks were inoculated with brain homogenate. Parasites were identified by electron microscopy and DNA sequencing. The antigen profile of the isolate was analysed using Western blotting. Pathogenicity was examined in BALB/c mice and transmission of the parasite during pregnancy was examined in Qs mice. RESULTS: The calf was seropositive for N. caninum and histopathological examination of sections of cerebrum identified lesions consistent with a very mild infection with N. caninum. The parasites isolated using tissue culture were identified as N. caninum, based on the sequence of the ribosomal DNA and electron microscopy. The antigen profile of the new isolate was similar to that of the NC-Liverpool isolate, but quite different from that of Toxoplasma gondii. In BALB/c mice inoculated with the new isolate, severe clinical signs developed in only three of ten infected mice, compared with six of ten mice infected with NC-Liverpool. Mild to moderate nonsuppurative encephalitis was observed in BALB/c mice infected with the new isolate, compared with mice infected with NC-Liverpool, that developed severe nonsuppurative encephalitis. Transplacental transmission of the isolate arising from an acute infection during pregnancy occurred in about 87% of pups. CONCLUSION: This is the first isolation of bovine Neospora caninum in Australia. This isolate, called NC-Nowra, appears to be a less virulent form and may prove to be a suitable candidate for vaccine development.

Pinocytic loading of cytochrome c into intact cells specifically induces caspase-dependent permeabilization of mitochondria: evidence for a cytochrome c feedback loop.

Previous studies introduced cytochrome c into intact cells via the disruptive techniques of microinjection or electroporation to provide support for the hypothesis that, in whole cells, cytochrome c release from mitochondria triggers caspase activation and other degradative changes. However, the types of measurements that could be undertaken with these techniques was limited. We used the simple and relatively gentle technique of pinocytic loading to demonstrate that, in intact cells, cytosolic cytochrome c specifically induced activation of caspase-3- and -9-like enzymes, and a loss of mitochondrial polarization coincident with an increase in mitochondrial permeability. Our results support the prediction from in vitro studies that activation of caspases-3 and -9 is downstream of cytochrome c release and provide the first direct evidence that, in whole cells, cytochrome c-dependent caspase-activation can exert a feedback effect to elicit mitochondrial permeabilization and collapse of the mitochondrial trans-membrane potential.