Killer germs on the loose
Will our new super drugs be up to the task of fighting these superbugs?
BY GREG CALLIGARO for YOU Pulse magazine
There’s a new spectre when it comes to global diseases: H5N1 influenza, commonly called avian influenza or bird flu. It’s a subtype of the influenza A virus that infects birds but it can also cause disease in humans.
It occurs naturally in many bird populations in Southeast Asia but is now spreading globally, killing tens of millions of birds and resulting in the culling of hundreds of millions more – including domestic poultry – to stem its spread.
So far only humans handling sick birds have become infected but if the virus mutates or reassembles into a strain that can effectively pass from one human to another we could have a global emergency on our hands.
In 2003 world-renowned virologist Robert Webster wrote in a report that ‘‘the world is teetering on the edge of a pandemic that could kill a large fraction of the human population’’.
This is no alarmist overreaction: the Spanish Influenza outbreak of 1918-1919, caused by a particularly virulent strain of influenza, is estimated to have killed 25-50 million people.
Deadly Ebola outbreak
And as recently as November last year the deadliest germ known to humankind, the Ebola virus, emerged again in Uganda from its unknown reservoir in the jungles of central Africa, killing nine out of every 10 people it infected.
Death comes painfully: the virus virtually dissolves internal organs within days, causing bleeding from every pore. There is no known cure.
Why are humans still so vulnerable to infectious disease when we have sophisticated antibiotics and keep hearing about antiviral breakthroughs?
Not long ago doctors thought they’d managed to bring infectious diseases under control for good. Smallpox had been eradicated, effective vaccines had been developed for polio and yellow fever and with the discovery of penicillin and other antibiotics treatment was available for ancient illnesses such as syphilis, leprosy and even the bubonic plague of the late Middle Ages.
Diseases such as diphtheria, whooping cough and tetanus seemed to belong to history books. It was only a matter of time, scientists believed, before we’d finally leave behind the dark times when microscopic invaders from an unseen world could threaten our existence.
Louis Pasteur, one of the fathers of the science of microbiology and the inventor of the vaccine for another dreaded virus, rabies, once boasted that one day every infectious disease would be as easy to beat.
Deadly infections threatening
But no one believes that any more. Despite the arsenal of medicines modern science can call upon in its fight against disease, deadly infections are still a threat to everyone everywhere.
Scientists at the Centers for Disease Control and Prevention (CDC) in the US warn that we’ve entered an age where ‘‘the spectrum of infectious diseases is expanding and cases of many infectious diseases once thought to be controlled are increasing’’.
Hardly a week goes by without a report in the media of some kind of outbreak – plague in India, ‘‘flesheating’’ Streptococcus in Britain, drug-resistant Staphylococcus in hospitals in the US, hard-to treat wound infections in soldiers returning from Iraq.
Closer to home we hear of a diarrhoeal epidemic in Delmas in Mpumalanga and an outbreak of a resistant bacterial infection in a neonatal intensive care unit in KwaZulu-Natal.
We also have our own version of Ebola: a virus called Congo-Crimean fever, carried by ticks, which – every few years, sporadically and unpredictably – emerges to kill farm workers in rural areas.
Public enemy No 1
HIV/Aids must surely be the infective disease emergency of our generation. The World Health Organisation (WHO) estimates HIV, which was discovered in 1981, has killed more than 25 million people – the majority in sub-Saharan Africa – making it one of the most destructive pandemics in recorded history.
It’s a particularly diabolical virus because, unlike Ebola which can kill in hours, HIV leaves its victims relatively well for several years – with plenty of opportunity to pass it on to others.
So far HIV has resisted all attempts to halt its spread using the usual strategy against viral infections: immunisation. The viral DNA mutates so easily and the proteins that coat the virus are so variable that researchers are still far from developing an effective vaccine.
Immune system under attack
Experts in infectious disease are especially fascinated by HIV because it attacks the one stronghold that normally holds armies of microscopic pests at bay: our immune system.
Infecting and killing battalions of specialised white blood cells called macrophages and lymphocytes, HIV weakens infected patients’ immune systems until they become vulnerable to any attack.
The result? A menagerie of opportunistic microbes that a healthy immune system would easily swat away swarm over the body’s defences and cause disease.
(This is an edited version of a story that originally appeared in YOU Pulse / Huisgenoot-POLS magazine, Autumn 2008. Buy the latest copy, on newsstands now, for more fascinating stories from the world of health and wellness.)