This is the first article in a four part series looking at how infectious diseases have influenced our culture and evolution, and how we, in turn, have influenced them.
In 2013, the World Health Organisation declared antibiotic resistance was a threat to global health security. It can seem hard to believe that in the 21st century infectious diseases remain such a profound existential risk. But this declaration highlights the ever-lingering threat of infectious diseases and our dependence on antibiotics to stave off their impact on human and animal health and industry.
It also reminds us to appreciate antibiotics as one of many advances in infectious diseases and public health during the past century, and reflect on some of the greatest, still persistent, infectious disease challenges facing us today.
Here we explore our past and present struggles with four of the most significant infectious diseases human beings have faced, some of the progress we’ve made in prevention and treatment, and possible future directions.
Tuberculosis (or TB) has been responsible for the death of more people than any other infectious disease in history; over a billion deaths in the past 200 years. Its origin is unclear, but it infects a number of other species, including cattle.
Today, about a third of the world’s population is thought to be infected with TB, in its dormant form. This means the bacteria is present but it’s controlled by the immune system, the infected person has no symptoms, and it can’t be spread to others. The bacteria will reactivate in a small proportion of people and they may develop symptoms including fever, sweats, weightloss, fatigue, cough, and haemoptysis (coughing up blood).
TB occurs in every country, including Australia, but mostly occurs in people born in countries where TB is more common, due to the reactivation of dormant TB infection. Patients with weakened immune systems due to chemotherapy, HIV or other medical illnesses are at higher risk of TB.
In 2015, there were 10.4 million new cases of TB, and 1.8 million TB-related deaths around the world?, with the vast majority of cases in developing countries. The infection and death rate have been declining internationally since the early 1900s.
Long before the availablility of treatment options, improvements in sanitation, housing, and vaccination led to a reduction in the rates of TB in some countries. But antibiotics made it a curable disease; without them, up to 70% of people with active infection die from TB.
But treatment is complicated, and typically involves taking four medications for two months, then two medications for a further four months. These medications are not without side effects, and can be poorly tolerated. Unfortunately, when medications are not taken or prescribed properly, the TB bacteria can become resistant to these treatments.
Treatment of resistant TB is much more complicated, takes longer, is more prone to failure, and often uses more toxic drugs. New rapid tests can diagnose TB, and whether or not the bacteria will be resistant to our first-line drugs.
Despite advances in treatment, tuberculosis continues to occur disproportionately in the developing world. Although progress is being made, ongoing and increased political and financial support is essential to ensure coordinated diagnosis, surveillance and care strategies, and universal access to these. Similarly, continued investment is needed for the development of new tools to detect and treat TB.