'Half of airport security trays' have traces of cold...

"Airport security trays carry more viruses than toilet surfaces," reports The Guardian. Scientists took samples from various surfaces at Finland's main international airport in Helsinki during the height of its 2016 flu season. They found that 4 out of the 8 frequently-handled trays tested were contaminated with traces of respiratory viruses such as common cold and flu.

They also found traces of viruses on children's toys in a play area, handrails for stairs, glass security screens at passport control, and on the chip-and-pin machine in the airport's pharmacy.

By contrast, none of the surfaces sampled in public toilets in the airport carried signs of respiratory viruses.

The methods used for sampling showed traces of viral genetic material, which isn't the same as finding live viruses capable of causing an infection. However, the researchers say their research shows the potential for passengers to pick up and spread infections through "hot spots" like airport security. This could be especially important during an international outbreak of disease, such as the 2009 swine flu pandemic.

There is no evidence that people exposed to the viral genetic material went on to develop an infection. That said, the researchers' suggestion that people should be encouraged to use alcohol hand disinfectant before and after security checks, to minimise the risk of infection, is sensible advice.

Where did the story come from?

The study was carried out by researchers from the National Institute for Health and Welfare in Finland, VTT Technical Research Centre Finland Ltd and the University of Eastern Finland, and the University of Nottingham.

It was funded by the European Union and published in the peer-reviewed journal BMC Infectious Diseases on an open access basis, so it's free to read online.

The Guardian and The Daily Telegraph gave good overviews of the study. However the Mail Online was arguably over dramatic, warning that "trays are covered in pathogens that can cause everything from the common cold and flu to pneumonia, bladder infections, SARS and even brain damage."

Only 4 of 8 trays tested showed any signs of virus. Although one tray showed signs of coronavirus, some types of which can cause SARS and other serious infections, most coronaviruses are not dangerous and cause only cold-like symptoms.

What kind of research was this?

This was a sampling study which tested for viral DNA in 90 swabs taken from surfaces, and 4 air samples. This type of study can give us a broad idea of which areas of an environment are most at risk of transmitting infections, but does not tell us how likely infection is.

What did the research involve?

Researchers mapped the standard passenger journey through Finland's Helsinki-Vantaa airport, looking at both arrivals and departures.

They collected samples weekly at 3 different time points (early morning, around noon and mid-afternoon, coinciding with peak travelling times) between the 4th and 17th February 2016. They swabbed 13 different surfaces and sampled the air in the security check area.

The samples were tested for viral nucleic acid (DNA or RNA) for a number of common respiratory viruses:

seasonal influenza A and B (which can cause flu)
respiratory syncytial virus (which can cause respiratory infections in children)
adenovirus (which can cause fever, coughs, sore throats, diarrhoea, and eye infections)
rhinovirus (which can cause the common cold)
coronavirus (which can cause respiratory infections)

What were the basic results?

Of 90 tests carried out, 9 (10%) showed signs of viruses. The most commonly found was rhinovirus (4 samples) followed by adenovirus (3 samples), coronavirus (3 samples) and influenza A (1 sample). Some samples had signs of more than 1 virus.

Of the sites sampled, traces of viruses were found in:

4 out of 8 samples of luggage security boxes
2 out of 3 samples of a child's plastic toy in the children's play area
1 out of 7 samples of handrails on stairs
1 out of 3 samples of glass dividing screens at passport control
1 out of 2 samples of the chip and pin machine in the pharmacy
1 out of 4 samples of air taken in the security check area

None of the samples taken from toilets, chair armrests, escalator handrails, luggage trolley handles, elevator buttons or check-in machine touch screen had traces of virus.

How did the researchers interpret the results?

The researchers said their research showed "respiratory virus contamination of frequently touched surfaces is not uncommon at airports" and that "plastic security screening trays appear commonly contaminated".

They say their research "helps in the recognition of hot spots for contact transmission risk which could be important during an emerging pandemic threat or severe epidemic." They also suggest the particular risk posed by security trays could be reduced "by offering hand sanitization with alcohol handrub before and after security screening" and by routinely disinfecting trays.

Conclusion

While the headlines may be alarming, when you look at the actual figures, it is perhaps surprising how few of the surfaces sampled by researchers were contaminated with respiratory viruses, given that the study took place during the height of the flu season.

The main finding, that plastic security trays are most likely to be contaminated, is interesting and could be useful in reducing pandemics of respiratory disease in future. Everyone getting on a plane goes through airport security, and most will need to use the trays provided to scan hand luggage. The high throughput and constant recycling of these plastic trays, which are not regularly disinfected, increases the chances that bugs can be spread from hand to hand.

The study has some limitations. The main one is the relatively small number of samples taken. For example, only 8 samples were taken from the hundreds of trays circulating in airport security. The results could have been completely different for another selection of 8 trays.

The sampling methods may not have been efficient, and the samples showed only presence of viral DNA or RNA, not actual live viruses. So the study can only give us a snapshot of what might be happening with virus transmission at an airport.

However, it's a reminder that good hand hygiene is important not just for preventing stomach upsets when using toilets, but also to reduce the chances of picking up colds and flu infections when out and about.

This is especially important in public places which have a high number of people passing through, such as airports. Find out more about how good handwashing can cut your chances of getting sick.