Estimating SARS-CoV-2 transmission parameters between coinciding outbreaks in a university population and the surrounding community

Prior studies suggest that population heterogeneity in SARS-CoV-2 (COVID-19) transmission plays an important role in epidemic dynamics. During the fall of 2020, many US universities and the surrounding communities experienced an increase in reported incidence of SARS-CoV-2 infections, with a high disease burden among students. We explore the transmission dynamics of an outbreak of SARS-CoV-2 among university students, how it impacted the non-student population via cross-transmission, and how it could influence pandemic planning and response. Using surveillance data of reported SARS-CoV-2 cases, we developed a two-population SEIR model to estimate transmission parameters and evaluate how these subpopulations interacted during the 2020 Fall semester. We estimated the transmission rate among the university students (βU) and community residents (βC), as well as the rate of cross-transmission between the two subpopulations (βM) using particle Markov Chain Monte Carlo (pMCMC) simulation-based methods. We found that both populations were more likely to interact with others in their population and that cross-transmission was minimal. The cross-transmission estimate (βM) was considerably smaller [0.04 × 10-5 (95% CI: 0.00 × 10-5, 0.15 × 10-5)] compared to the community estimate (βC) at 2.09 × 10-5 (95% CI: 1.12 × 10-5, 2.90 × 10-5) and university estimate (βU) at 27.92 × 10-5 (95% CI: 19.97 × 10-5, 39.15 × 10-5). The higher within population transmission rates among the university and the community (698 and 52 times higher, respectively) when compared to the cross-transmission rate, suggests that these two populations did not transmit between each other heavily, despite their geographic overlap. During the first wave of the pandemic, two distinct epidemics occurred among two subpopulations within a relatively small US county population where university students accounted for roughly 41% of the total population. Transmission parameter estimates varied substantially with minimal or no cross-transmission between the subpopulations. Assumptions that county-level and other small populations are well-mixed during a respiratory viral pandemic should be reconsidered. More granular models reflecting overlapping subpopulations may assist with better-targeted interventions for local public health and healthcare facilities.

Fire, climate change and biodiversity in Amazonia: a Late-Holocene perspective

Fire is an important and arguably unnatural component of many wet Amazonian and Andean forest systems. Soil charcoal has been used to infer widespread human use of landscapes prior to European Conquest. An analysis of Amazonian soil carbon records reveals that the records have distinct spatial and temporal patterns, suggesting that either fires were only set in moderately seasonal areas of Amazonia or that strongly seasonal and aseasonal areas are undersampled. Synthesizing data from 300 charcoal records, an age–frequency diagram reveals peaks of fire apparently coinciding with some periods of very strong El Niño activity. However, the El Niño record does not always provide an accurate prediction of fire timing, and a better match is found in the record of insolation minima. After the time of European contact, fires became much scarcer within Amazonia. In both the Amazonia and the Andes, modern fire pattern is strongly allied to human activity. On the flank of the Andes, forests that have never burned are being eroded by fire spreading downslope from grasslands. Species of these same forests are being forced to migrate upslope due to warming and will encounter a firm artificial fire boundary of human activity.

Indigenous women's perceptions of breast cancer diagnosis and treatment in Queensland

OBJECTIVE

To identify social, structural and personal factors among indigenous women in Queensland associated with the detection of breast cancer, and the treatment and post-treatment care and support of cancer.

METHODS

Qualitative research including interviews, case studies and focus group discussions were conducted, among Aboriginal women and service providers in urban, rural and remote areas of Queensland over nine months in 1998/99.

RESULTS

A range of factors were identified as influencing women's willingness to perform BSE, receive screening mammograms, and receive and complete treatment compared to the non-indigenous population. Personal history of health services, provision of information about mammography, the cost of treatment and care, and availability of personal support, all influenced women's willingness to access services and maintain treatment. Indigenous women in Queensland experience various barriers to effective and appropriate detection, treatment and care of breast cancer.

CONCLUSION

Barriers to diagnosis, treatment and care can be addressed by increasing women's awareness of breast cancer and the benefits of preventative health behaviour, and improving the quality and appropriateness of health care and counselling services for Indigenous women and their families.

IMPLICATIONS

Indigenous women's knowledge and practice relating to the early diagnosis and prevention of breast cancer may improve through outreach work with women, to encourage their confidence in preventative health. Women's commitment to preventive health will also be enhanced by improved quality and access to health care, and improved relationships between practitioners and patients.