The blog

As we approach the end of the summer holiday season, I’m writing this blog whilst sitting on a plane on the way home from a conference. I can hear the continuous ‘whoosh’ of the air conditioning system and can’t help but wonder what I might be breathing in. I know for a fact that Lucy G is suffering right now from a virus that she thinks she caught whilst on a plane journey she made recently.

I expect you’ve read about the Ryanair flight that was delayed and passengers prevented from leaving the plane for some time due to a suspected case of chicken pox on board the plane.

Read the full news story

There has also been a case of TB being transmitted through commercial air travel, so how are we, as passengers to avoid infection? The increase in availability of travel across continents means that diseases which were once restricted to certain climates or continents are increasingly being seen elsewhere. The case of an outbreak of SARS aboard a Hong Kong flight to Beijing in 2003 is an illustration of the contribution of commercial air travel to the spread of newly emerging infectious disease and may also apply to bioterrorism agents. So it seems that the ease and availability of air travel could be a cause of public health concern.

That said, according to an article in the Lancet, most commercial aircraft re-circulate 50% of the air in the cabin and this re-circulated air is passed through HEPA filters with a particle-removing efficiency of 99.97% at the 0.3 micron level. This prevents bacteria and fungi from passing through the filters and is likely to do the same for viruses which are usually transmitted via droplets which are larger than 3 microns. Furthermore, no peer-reviewed scientific investigations have reported that air travel is any more risky in terms of the spread of infectious disease than other modes of transport or, with reference to being in close proximity to many other people, working in office buildings.

Click here to read the Lancet article
(you will need a subscription to the Lancet in order to view the full article)

So, is air travel dangerous from an infectious disease perspective? Should we be concerned about the part that travel plays in the global spread of infectious disease? But most importantly of all, have you had a nice holiday?

In the 1980s an iconic advertising campaign was launched in an attempt to halt the spread of HIV and to provide the public with information about the infection. TV adverts shocked the UK and a leaflet was delivered to every home. The campaign was a huge success, not just for HIV but for other sexually transmitted infections (STIs). Cases of gonorrhoea fell from 50,000 in 1985 to 18,000 in 1988 and syphilis dropped from 1500 cases a year in the mid 1980s to 150 in the mid 1990s. New HIV diagnoses fell by a third in three years. In 1985-6 and 1992-3 the government spent £73 million on HIV awareness campaigns.

The focus has since shifted to other STIs. The Terrence Higgins Trust launched “Get it checked, Get back out there”. The campaign targets gay men and focuses on reducing the rates of syphilis, gonorrhoea, Chlamydia and herpes infections. Posters depicting men who show signs of infections will be displayed in gay bar washrooms, on the roadside near gay venues, in phone boxes near London gay venues, in London Underground stations and in cigarette kiosks on Manchester’s Canal Street.

Get it checked. Get back out there

The Department of Health has spent £4 million on the “Condom: Essential Wear” campaign, which complements the existing campaigns “R U Thinking?” and “Want Respect? Use a Condom.” According to a survey, 90% of girls and 70% of boys have “pulling pants” but only 20% carry condoms. Images depict couples wearing clothing labelled with STIs, including a “gonorrhoea” necklace and “Chlamydia” underwear. The campaign has been launched on TV, in magazines, on the radio and online.

Condom: Essential Wear

The Department of Health campaign has been criticised because of its budget; some people think the money could be better spent elsewhere. There has been concern that the UK’s sexual health clinics are already overstretched and may not cope with an increase in people requesting tests. The aim of the campaign also poses another problem: an increase in testing will inevitably lead to an increase in diagnoses. Last week, the Health Protection Agency reported an increase of 6% in new diagnoses of STIs, from 375,843 in 2006 to 397,990 in 2007. New Chlamydia diagnoses increased by 7% but this is probably because screening has increased by 10% over the same period. The number of herpes diagnoses increased by 20% but this is also likely to be due to an improvement in testing.

Perhaps the real measure of success will be awareness. Before the HIV campaign of the 1980s, people believed HIV could be transmitted by kissing, sharing bathing water or via toilet seats, ideas that are relatively uncommon now. In November 2007 Genevieve Clark, director of communications at the Terrence Higgins Trust, said: “Our research found that one in ten men think Chlamydia is a flower.” Let’s hope the current campaigns squash this myth!

According to a survey commissioned by the Society for General Microbiology, 88.6% of people asked knew that microbes can be both harmful and beneficial. [Read the results here.] This is good news, especially considering the plethora of adverts warning us to disinfect every corner of our lives or else be infected with a deadly pathogen (see my blog, “Adverts give microbes a bad name”). Logic says there must be a force working in opposition to the bad ads, and there is: the good ads.

In the last few years, probiotic products have really taken off in the UK; now an estimated 4.5 million people consume a daily probiotc supplement, such as a yoghurt or drink. This increase has been reflected in the recent burst of TV adverts telling us why bacteria are so important. Yakult recently launched their “Planet You” promotion at a cost of £5.5 million, employing Euro RSCG London to “produce a campaign backed up by science”.

Watch the Yakult advert »

I will be the first to admit that certain aspects of this dietary revolution irritated me to begin with. Until relatively recently, scientific evidence had been questionable, and claims that “Bifidus digestivum” could cure our ills seemed suspicious. But research into probiotics and prebiotics has grown rapidly and is now well established and respected. Yakult’s TV advert is the first ever to show such an image of the human intestine and has been praised by advertisers and scientists alike. The scientific content is sound (give or take “a bacteria” here and there). But perhaps the most important thing is that “friendly” bacteria are given a good name (Lactobacillus casei Shirota in this case).

In this month’s podcast, we talk to Professor Glenn Gibson and Professor Bob Rastall from the University of Reading about the science behind probiotics and prebiotics. Since recording the interview, my shopping list has grown… let us know what you think!

Last October, a Dettol advert was banned for extrapolating evidence to claim “Fact: your chopping board harbours fifty times more bacteria than your toilet seat.” It exaggerated the dangers posed by bacteria on chopping boards, based on a 2004 study of five houses in Hertfordshire, each complete with a toddler.

The decision made by the Advertising Standards Authority to ban the advert was praised by people who feel that as consumers we are terrified into buying products to sterilise our lives. I am one of them. Having studied microbiology, I am a great believer in the hygiene hypothesis, the theory that without exposure to antigens, including the 99.99% of bacteria killed by Dettol Surface Cleanser, the immune system is less able to fight infection and allergies develop more readily. In fact, research recently showed that kids who play in dirt are happier thanks to soil-dwelling bacteria that produce ‘happy molecules’.

According to a fellow objector, the nation is “crippled with paranoia” because of “a few thoughtless idiots that give all bacteria a bad name.” Writing on tellyads.com about the Oust 3 in 1 advert, he admits “I’m so concerned about one day picking up the TV remote and bacteria eating my hand off that I’ve commissioned a crop-sprayer to fly over my house twice a day to squirt a few thousand gallons of Oust all over it.”

Watch the Oust advert »

Sitting at home, I am constantly reminded that if I don’t protect and disinfect my chopping board/toilet seat/curtains/bath sealant I’m in grave danger of contracting a life-threatening MRSA infection. But let’s be sensible. This isn’t going to happen. In fact, I’m far more likely to pick up a nasty stomach upset after failing to wash my hands after chopping up raw chicken, or for putting raw meat on the top shelf of the fridge in the perfect position to dribble all sorts of food poisoning microbes on the cheese. In this case, surely it would be far more effective, easier and cheaper to learn some simple food hygiene practices. So here are my top 3 tips:

1. After chopping raw meat or poultry, clean your hands, the chopping board and the knife.
2. Cook food properly.
3. Keep your fridge clean and tidy, with raw meat in sealed containers at the bottom.

How accurate is the news? A question that I’m sure we all ask ourselves from time to time.

From the point of view of science in particular, things are definitely improving. To bridge the gap between scientists and journalists the Science Media Centre (SMC) was established in 2002 (www.sciencemediacentre.org). The SMC does an excellent job of matching journalists with experts, reacting to news stories by getting the right people to speak on the right topics and helping Press Officers and Scientists from all disciplines publicise their work without a hint of hype or sensationalism. In my opinion there has been a dramatic improvement in the reporting of science in the media and things continue to improve.

However, I can’t let the fact that I witnessed MRSA being called virus in a daily broadsheet pass without comment as this is the kind of mistake that makes by blood boil! So, to clear up this issue, here’s a basic microbiology lesson on the difference between a bacterium and a virus. To begin with, bacteria and viruses are very different in size – viruses are much smaller than bacteria which in turn are much more complex than viruses. Bacteria are living organisms that can reproduce on their own and therefore they have all the necessary ‘equipment’ with which to do so. They have a cell wall, cell membrane, cytoplasm, ribosomes, plasmids and chromosomal DNA. They also, in some cases, have flagella to help them move around. Viruses on the other hand have very simple structures consisting of a protein coat which contains either DNA or RNA. Some also have an outermost envelope but otherwise that’s all a virus has. These differences are most obvious when we look at the way viruses and bacteria reproduce. Viruses only contain the genetic material necessary for reproduction, they do not contain any of the mechanistic tools to enable them to do so, whereas bacteria can reproduce independently of other living organisms. Viruses need to invade the cells of a ‘host’ organism e.g. human, either by attaching to the cell and injecting their DNA or RNA into the cell, or by being swallowed by a host cell. They then use the reproductive machinery of the host cell in order to replicate inside the cell. It is the difference between bacteria and viruses that explains why antibiotics don’t have any effect against the common cold – or any other viral infection for that matter.  

So there you have it – the difference between bacteria and viruses. If you have any comments on the difference between these microscopic organisms, do feel free to post a comment here, we’d love to hear from you.

I know a some people who feel as passionately about the accurate reporting of science in the media as I do. So if you’re one of them then let us know your viewpoint by posting a comment here. We’d love to hear from you.