From statistics on Australian confinements during the period 1944-63 it seems that the following conclusions can legitimately be drawn:(1) The proportion of multiple births increases with increasing age of mother up to about age 37, turns, and decreases thereafter.(2) The proportion of multiple births increases with increasing age of father up to about age 34-38 and is fairly constant thereafter.(3) The variation with age of father, however, only arises because of the high correlation with age of mother which is the determining factor.(4) The proportion of multiple confinements increases with birth order. This effect holds for all ages of mother except those over 40 where there is no significant variation.(5) The proportion of multiple confinements decreases from the first year of marriage to the second, then increases steadily to a maximum after about 15 years of marriage and then decreases slightly.(6) The proportion of binovular twins increases steadily with increasing age of mother up to about age 37, turns, and thereafter decreases steadily.(7) The proportion of monovular twins increases slightly with increasing age of mother up to about age 37 and is fairly constant thereafter.(8) From the small amount of data it appears that the proportion of triplets also increases with increasing age of mother.
Using Australian records of human births for the first six decades of the twentieth century, the proportions of male and female births are studied in relation to the mother's age, the father's age, the parents' ages in combination, and certain other factors. The principal data used relate to the years 1931-55, during which over 3 million children were born, yet even so the significant features are not easy to discern.Masculinity tends to fall as the age of either parent increases. But it is only average or below if one parent is old while the other is young. For high masculinity, both parents must be young.The Australian data are available in a form which enables the sex ratio to be studied also in relation to (a) the season of the year; (b) urban and rural areas; (c) the different states of the Commonwealth; (d) births inside and outside marriage; and (e) single and multiple births. When the influence of the parents' ages is eliminated, however, it does not appear as though the sex ratio varies significantly with any of these factors.
Household transmission plays a key role in the spread of Covid-19 through populations.In this paper, we report on the transmission of Covid-19 within households in a metropolitan area in Australia, examine the impact of various factors and highlight priority areas for future public health responses. We collected and reviewed retrospective case report data and follow-up interview responses from households with a positive case of the Delta Covid-19 variant in Queensland in 2021. The overall secondary attack rate (SAR) among household contacts was 29.6% and the mean incubation period for secondary cases was 4.3 days. SAR was higher where the index case was male (57.9% vs. 14.3%) or aged ≤12 years (38.7% vs. 17.4%) but similar for adult contacts that were double vaccinated (35.7%) and unvaccinated (33.3%). Most interview participants emphasized the importance of clear, consistent and compassionate health advice as a key priority for managing outbreaks in the home. The overall rate of household transmission was slightly higher than that reported in previous studies on the wild Covid-19 variant and secondary infections developed more rapidly.While vaccination did not appear to affect the risk of transmission to adult subjects, uptake in the sample was ultimately high.
Household transmission plays a key role in the spread of Covid-19 through populations. In this paper, we collected and analysed retrospective case report data and follow-up interview responses from households with a positive case of the Delta Covid-19 variant in Queensland in 2021. The overall secondary attack rate (SAR) among household contacts was 29.6% and the mean incubation period for secondary cases was 4.3 days. SAR was higher where the index case was male (57.9% vs. 14.3%) or aged ≤12 years (38.7% vs. 17.4%) but similar for adult contacts that were double vaccinated (35.7%) and unvaccinated (33.3%). Most interview participants emphasized the importance of clear, consistent and compassionate health advice as a key priority for managing outbreaks in the home. While vaccination did not appear to affect the risk of transmission to adult subjects, uptake in the sample was ultimately high.
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