As David Cameron warned that antibiotic-resistant superbugs are threatening to return medicine to "the dark ages", here are seven diseases and viruses that have been fighting back against drugs and posing a global health risk.
The drug chloroquine was supposed to rid the world of malaria, but resistance grew and by the late 1970s it was useless. The pattern has since been repeated with every other safe drug for the disease. The last great hope was artemisinin, but resistance to that has now been reported in Cambodia. Patients are now being given clever drug combinations to slow resistance, but this merely buys us time while scientists develop new drugs.
The outlook for HIV patients improved dramatically in the 1990s with the arrival of highly active antiretroviral therapy (HAART), but drug resistance is now developing in the HIV virus. Although the numbers of people with drug resistant infections are relatively low, they are rising rapidly - for example by 5% a year in South Africa.
TB should be treatable within six months with a course of antibiotics including isoniazid and rifampicin. But doctors have been foiled by the emergence of multidrug-resistant TB (MDR-TB), to the even worse extensively drug-resistant TB (XDR-TB) and now even to total drug-resistance (TDR-TB), which has only officially been confirmed in India. Resistance to TB has reached a global scale with XDR-TB reported in 92 countries.
This sexually-transmitted infection was once easily treatable with common antibiotics such as penicillin and tetracycline. But the bacteria behind the disease have developed such high levels of resistance that there is only one drug left that can treat it. Even this antibiotic, ceftriaxone, is now becoming less effective, sparking fears that the STI could spread throughout the population.
It’s likely you have never heard of this common bacterium, but Klebsiella is among a group of six pathogens known as ESKAPE that are increasingly being acquired in hospitals. While the threat of MRSA declines, these pathogens are seizing the opportunity. The World Health Organisation has warned that routine hospital visits or treatments could result in these previously treatable bacteria having fatal effects.
Routine vaccination against typhoid means it is not a disease we fear in the UK, but the disease still affects 21.5 million people each year in the developing world. The risk extends to those taking exotic trips, especially to South Asia where resistance to multiple antibiotics is increasing most. Doctors recommend that the key is to get vaccinated before getting onto the plane.
Resistance has not yet emerged for bacterial disease such as diphtheria or syphilis - some may think they don’t even exist anymore - but according to Public Health England, syphilis rates have been increasing in the UK since 1997. This STI is currently treated by a single injection with penicillin, but resistance against this antibiotic has developed in other diseases. If it happened again, the rates of infection could rise much further.
This information was supplied by Professor Mike Turner, Head of Infection and Immunobiology at the Wellcome Trust.