Parasitoid wasps are nightmarish critters of death and manipulation. For all the times you’ve been stung by a wasp, just be glad it didn’t lay its carnivorous unborn into your still living flesh. Evolution has ‘gifted’ us a huge number of such insects, which happily prey on as large a number of different bugs to both incubate their eggs and eventually provide the newly hatched young with a live-in shelter to eat their way out of.
“Mike?!” you yell, “Why are you ruining our brains forever with this? Where are the viruses?!”
Worry not, viruses are at work here. In fact, this article deals with just one such virus story (I’ll save the other for a later write-up).
In brief, because you should dive into the linked article:
Wasp injects ladybird (ladybug) with an egg. Ladybird carries around egg, which later hatches and eats its way out of the ladybird. Wasp wraps itself in a cocoon to develop into an adult and the still living (but presumably now-porous) ladybird guards the cocoon from predators. Why? Because a virus, named D. coccinellae Paralysis Virus, or DcPV, that lives in the wasps and their eggs, infects the brain of ladybirds and turns them into zombie guards. Nature. You are scary.
OK, let’s get serious. A report into what we know about Ebola transmission has been published this week, and the media has leapt on to the authors’ opinion that the virus might spread by air as well as by contact. I don’t see a problem with the media’s interpretation of the report: the news seems to be carrying the salient points made by the piece. But the fact of the matter is that the evidence to back up aerosol transmission of Ebola just isn’t there. We know that people get infected when they come into close contact with the very sick and/or dying: people leaking virus-laden fluid into their immediate surrounding environment.
The possibility of transmission of virus cast into the air by the coughing sick – possible, but paling in comparison to the aforementioned infectious fluid – does not match up to the fear of a ‘Hollywood-style’ virus epidemic. The sick spread the virus to one or two people by close contact, they do not infect dozens by lacing the air with virus particles.
Could the virus evolve to use a different route of transmission though? Suddenly infecting through the air rather than by contact? No. A scene in the movie Outbreak, in which scientists crowd around an electron microscope image of an Ebola-like virus, before and after the “evolution of hair-like molecules” which “enable the virus to spread through the air” is firmly lodged in fiction (for the record, despite being objectively terrible, that movie is ace).
This topic is deserving of full articles to explain this reasoning and the outbreak as it stands, and so I defer to two:
- Tackling the question of Ebola as an airbourne pathogen – “Ebolavirus will not become a respiratory pathogen”
- Thoughts on the reality of the outbreak as it stands – “VDU’s blog: Ebola virus disease: obliterating a variant and stalled case decline…”
Finally, because choice of language is more important than we think, a small piece on ditching the term ‘pathogen’. This article isn’t virus-centric, but that’s really the point. We focus on the bugs – the “pathogens” – when we research disease, because we hold them up as the reason for the illness. But in reality, disease isn’t a one-way street. Our immune systems are often responsible for most of the damage done to us during infection, and some people can be asymptomatically infected with viruses, bacteria or fungi, when others become desperately ill.
The term pathogen isn’t going anywhere, but if we think about the pathology of infection a little more holistically, perhaps we’ll make better progress eliminating it.