Polio: next on the disease hit-list
With Smallpox confined to the annals of history, can't we do this again with other diseases? One virus we're closer to eradicating than ever before is Polio, which can cause fatal paralysis in victims. Jonathan Ball is Professor of Molecular Virology at the University of Nottingham and he explained to Chris Smith why polio is a good candidate for eradication.
Jonathan - Well there are two main things that we really look for in a virus that could be eradicated. The first is that we have an effective vaccine, so vaccinations are really key to generate immunity in the population that protects them from future infection. The other key thing is the fact that this is a virus that only infects humans and so there's not a massive animal reservoir out there that we have to worry about where the virus can continue to spill out and infect humans.
Chris - What progress has been made so far towards getting rid of polio?
Jonathan - There's been fantastic progress. So, towards the end of the 1980s, WHO decided that this was really something we could achieve, so they ramped up vaccination efforts and so it's important to vaccinate young children. Since the advent of the vaccination programme, we've seen huge decreases in the number of polio cases. We're left, at the moment, with only two countries where the virus is what we call endemic, so that means the virus is circulating in those human populations unhindered and those two countries are Pakistan and Afghanistan. Some of the problems that we have with that, because you have virus circulating in those countries, it means that occasionally that virus can be exported to other parts of the world. So, we saw recently the virus being exported from those regions into Syria with insurgent fighters, and then that virus spilt over into Israel, so it's really difficult to control.
Chris - Why are both of those countries hotspots for polio still?
Jonathan - The bottom line is that these are countries where there's a lot of civil unrest, particularly the northern parts of Pakistan and, of course, Afghanistan. There's huge problems with civil unrest, with war, etc., a wonderful breeding ground for viruses and it means it's very difficult for people to carry out these vaccination programmes. If we take Pakistan, for example, this was a country where we thought Osama Bin Laden was holed up and, in fact, as it turns out that is where he was holed up but the Americans, the CIA, apparently set up some kind of spoof vaccination programmes. This was hepatitis B vaccines, but what they did was they recruited a doctor who set up these vaccination programmes to try and get DNA samples so that they could see whether or not Osama Bin Laden and his family were living in the place that they thought he was holed up. And that caused mistrust in Pakistan and, therefore, they felt that these vaccination programmes were a weapon of the west. So they were very, very cautious and very suspicious of the vaccination people and, indeed, many of them lost their lives trying to carry out vaccinations in that area. Thankfully, things seem to be resolving and the programmes are going full steam ahead.
Chris - Is it looking promising them? Do you think that, notwithstanding those constraints and those socio-political problems, that actually we're going to prevail and we will see the end of polio?
Jonathan - I think so, but it really is a problem that has to be nailed because if you have any virus which is circulating, that poses a huge risk, certainly to surrounding countries but we travel a lot and people travel and, therefore, the virus can travel. So eradication, it really has to be full steam ahead otherwise we'll see this virus smoldering on and it will spread.
Chris - Can we apply the learning, which we have gained from the eradication of smallpox, from the near eradication of polio and turn our attention to other viruses which are big health threats? What else is on your wish list of potential viruses to get rid of?
Jonathan - Well the two that spring to mind immediately; the first one is HIV and the approach there isn't vaccination. We know that this is a virus that has being incredibly difficult to develop a vaccine and so what the United Nations are hoping to do is to be able to eradicate this virus through treatment. So, that's to treat people who are infected so that they can no longer spread the virus because we know that the virus spread is related to how much virus is circulating or being produced in a person and, therefore, by treating them they hope to reduce the amount of virus and, therefore, reduce the risk of onward transmission, and also to use drugs to prevent infection. It's a very ambitious aim; they hope to eradicate the virus within the next 15 years and time will tell if we achieve that.
But the other virus that really springs to mind is rabies virus, and this is a virus that could be eradicated through vaccination...
Chris - But rabies is carried by animals as well, isn't it? So, isn't that against the rationale that you put forward earlier that you need something to be a human infection exclusively to get rid of it?
Jonathan - Yes, well spotted. Really the key here is we couldn't imagine eradication in those animal reservoirs, or certainly not in bats, but in terms of classical rabies which we see very often in places like Africa, South America and also the Asian Continent. This is a virus that circulates in mammals, for example, dogs, and foxes, and wolves and things like that. It is possible to eradicate that virus because we know that there are vaccinations programmes that have worked in the past. I can think of vaccination programmes in north Germany, also in Scandinavia where they were able to lace food baits with rabies vaccine, leave it out for the wild animals to eat and when they were eating this free meal they became vaccinated and so they've been able to eradicate the virus from the wildlife populations and, therefore, you reduce the risk to humans. But any virus for which we have an effective vaccine, should really be on our radar for eradication.