Despite living in relative comfort, by 19th-century standards, in a rural parsonage in Haworth, Charlotte, Emily and Anne - as well as their less famous siblings - succumbed to some of the infectious diseases that characterised the Victorian age.

The Bronte siblings were mainly raised by their father Patrick, a clergyman who outlived all of his children and who seemed to enjoy the robust health that his family did not. His wife, Marie, died of uterine cancer at the age of 38.

Two elder sisters, Maria and Elizabeth, died of tuberculosis in 1825, when they were boarding, along with Charlotte and Emily, at a school for the daughters of clergymen in Cowan Bridge.The damp conditions at the school were said to have played a role in their susceptibility to the illness.

Patrick's only son, Branwell, died in 1848 aged 31. Although he also suffered from tuberculosis, he was a heavy drinker and opium user, which left him in poor health.

Emily died just four months later after catching a cold at Branwell's funeral. She also developed complications from tuberculosis, and was just 30 when she passed away.

Anne, the youngest sibling, was 29 when she died a year after Emily. She, too, had tuberculosis and passed away during what was supposed to be a restorative trip to Scarborough.

Charlotte remained at the parsonage in Haworth with her elderly father, who was blind by this time, and in 1854 married Arthur Bell Nichols, Patrick's curate. Within nine months she was dead at 38 after developing severe morning sickness during early pregnancy. Although tuberculosis is given as a cause of death on her death certificate, medical professors subsequently researched her condition and concluded she was suffering from hyperemesis gravidarum, a condition that is treatable with fluid replacement drips today. In the 19th century, however, women were unable to eat or drink and could die from malnutrition and dehydration. At the time, this side-effect of pregnancy was poorly understood.

Although life expectancy was significantly lower in the first half of the 19th century than it is now, the family lived in a large and comfortable house, were affluent by local standards, and spent most of their time away from the poor sanitation and overcrowded slums of nearby cities such as Bradford. Yet for not one sibling from a large middle-class family to reach the age of 40 was unusual.

Bronte experts, however, have identified a possible cause of this high mortality rate which would mean the unsuspecting family were living in a death trap.

Haworth's drinking water, they believe, came from springs which were contaminated by rainwater that had soaked through the church graveyard - which was close to the parsonage where the Brontes lived. Long-term exposure to the bacterial infections this caused could have weakened the constitutions of the siblings and those of their neighbours, whose average lifespan was only around 26.

Charlotte also made reference to the poor diet she had experienced during her time at school in Cowan Bridge, suggesting the siblings may have suffered from malnutrition as children, which would have further weakened their health and development - although as adults, they were comfortably-off enough to enjoy a diet that was varied by the standards of the period. All of the sisters were very short in stature.

At the time, 'consumption' was not thought to be a disease which passed between those living in close proximity to one another. The Bronte sisters' deaths were portrayed as the result of melancholy and grief - that they literally just wasted away after the passing of the previous tragic family member. Now, of course, we know how easy it would have been for them to infect each other with the killer disease.

This is why the Bronte sisters died so young