Why was life expectancy lower in medieval Europe than now in Australia

Why was life expectancy lower in medieval Europe than now in Australia? In medieval Europe, people did not fully understand the importance of keeping clean and healthy, so due to the lack of proper hygiene and diet, diseases were very common. Common illnesses included dysentery, cholera, typhoid fever, chicken pox, measles, and plagues (the Black Death for example). The bacterium Yersinia Pestis was discovered in the late 1800’s, so that means that before that time people had poor knowledge about bacteria and germs. Poor people in medieval Europe (80% of the population), washed in a cold dish of water, so for those people personal hygiene was basic. A long hot bath with scented oils, perfumes, and herbs were used by the wealthy to cleanse themselves. Everyone in medieval Europe only had baths once a week or less, because it was difficult to collect water from nearby rivers. Both the rich and the poor occasionally cleaned their teeth with a cloth that had mixtures of herbs and ash. The towns people lived in were usually dirty with rubbish and sewage everywhere, people wore rough clothing that had living infected insects in the material. Also, people usually drank dirty water and ate infected foods, which lead to health issues like diarrhoea. Due to the lifestyles of medieval people, health issues were more common, and their life expectancy was lower. Also, the knowledge about health has grown since then, and more scientific based medicines are now available.