Kevin McCracken: Humanity's long dance with infection

Polio has returned to Syria where about 500,000 children are not immunised because of the civil war. Photo / AP

Opinion

Ability of pathogenic microbes to survive drugs and rise of new infections alarming, says Kevin McCracken.

Reports of the first New Zealander to have contracted a "superbug" that is resistant to all antibiotics are a sad but timely reminder of the growing worldwide threat of antimicrobial resistance (AMR) - that is, the ability of pathogenic microbes to survive exposure to drugs that previously would have effectively eliminated them.

The victim, a Wellington teacher, was extremely unlucky in contracting such a relatively rare and aggressive pan-resistant organism (a bacterium known as KPC-Oxa 48), but the danger of AMR shouldn't be gauged by this rarity. AMR is a growing problem across a range of dangerous micro-organisms and, unless controlled, threatens the prospect of a return to a world without effective drug protection against many serious infections - ie, a new post-antimicrobial era.

In our age of enormous international mobility the danger of AMR is also truly global. Exemplifying this globality, the bacterium (Klebsiella pneumoniae) in the New Zealand case is believed to have been contracted while the person was in Asia.

Leading well-known diseases for which drug resistance is a major issue include tuberculosis, malaria, gonorrhoea and influenza. It is also a problem for a range of hospital-acquired infections (HAI) (eg, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Clostridium difficile, and Pseudomonas aeruginosa).

Apart from the serious threats they pose to personal and community health, resistant infections also carry a large economic impost. Treating extensively drug-resistant tuberculosis (XDR-TB), for example, has been estimated at several hundred thousand dollars a case. It is estimated HAIs affect about 6 per cent of all patients in Australia and take up almost two million bed days a year.

The irony of AMR is that it is a problem largely of our making. Bacteria, viruses, protozoa and other pathogens by nature try to adapt and outwit antimicrobials, but our often unwise use of such drugs has been responsible for helping accelerate the development of resistance. The widespread inappropriate prescribing of antibacterial drugs for viral infections, the failure to complete prescribed courses of medication, poor quality drugs in many developing countries, and the use of antibiotics as growth promoters in livestock production are all helping hands we unthinkingly give microbes.

AMR, however, is not the only reason to never underestimate the microbial world. Another threat is the ongoing emergence of completely new infections. HIV/Aids is the most obvious example of this in recent decades, followed by the scare of the Sars epidemic in 2003. But the list of serious new microbial threats goes alarmingly beyond these two examples, the catalogue for just the last few years including the still puzzling Sars-like coronavirus MERS-CoV that first appeared in Saudi Arabia in 2011, and the new avian influenza A(H7N9) virus that has emerged in China this year.

A majority of new human infections are "zoonoses", jumping the species barrier from other animals.

Also, there are many infectious threats that years ago seemed to be on the way out, but have subsequently re-emerged as significant health problems for large numbers of people around the world.

Malaria and tuberculosis are good examples of these. As noted above, drug resistance has become a major factor with these diseases. Their resurgence, though, also owes quite a deal to complacency stemming from early post-World War II gains against the diseases and the international eradication effort being allowed to ease off.

Given an opening pathogens will invariably exploit human vulnerabilities. Confirmation of polio among children in civil war-ravaged Syria at the end of last month perfectly illustrates that opportunism. Polio had not been reported in Syria since 1999, but the upheaval of the lengthy civil war has given the disease an opening with around half a million Syrian children now not immunised.

A concerted international eradication campaign over the past quarter century has polio on the verge of becoming only the second human infectious disease (after smallpox) to be eliminated globally. The disease is now endemic in only three countries - Afghanistan, Pakistan and Nigeria - and cases have decreased from around 350,000 in 1988 to 223 reported cases last year. But applying the final knock on the head of the disease is proving difficult and until that is achieved children worldwide are at risk. Unfortunately "health terrorism" in the shape of attacks on polio vaccine workers has hindered eradication efforts in Pakistan and Nigeria.

The Syrian cases are just one of several wildfire outbreaks this year. Some countries in the Horn of Africa with weak political and health infrastructures have also experienced polio outbreaks. As well, wild polio virus has been isolated in sewage samples in Egypt, Israel and the Palestinian territories over the past 12 months. Genetic analysis has pointed to the Syrian outbreak being linked to the Egyptian polio virus, which in turn has been linked to Pakistan in an unfortunate illustration of the global nature of health.

Back in the 1960s there were some bold statements by leading Western public health specialists that the battle against infectious disease was essentially over and won. Unfortunately nothing could be further from the truth - in both poor and rich countries. Humanity's "long dance with infection" is far from over.

Dr Kevin McCracken is a population health specialist and Honorary Fellow at Macquarie University, Sydney, Australia. He recently co-authored Global Health: An Introduction to Current and Future Trends (Routledge, 2012).