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It was whilst I was reading around the subject of the massive volume of viruses and bacteria found in our water supplies and in the oceans of the world, that I thought I’d also check out what organisms might be found in the air that we breath.
Two things brought this into my mind - firstly, it’s winter here and the wild winds are blowing in from the Indian ocean as I tap away at the keyboard, the rains are falling and after a long hot summer, the air feels clean and pure ... but after what I’d read about the what’s lurking in the ocean, I began to think “how clean and how pure”. The second thing that winter always reminds me of is that of being a little kid growing up in the UK and after the traditional British Sunday bath - and because I was the youngest, I was always the last to have my bath - my Mum always used to say “Don’t you dare go outside with wet hair because you’ll catch your death of cold”. Apart from being linguistically incorrect, I could never imagine that it was possible to be infected by a virus from the cold air through my wet hair! And in fact, my dear Mum’s age old adage has no basis in fact, but does seem to have a colourful history. That’s because if you go back just under a couple of hundred years ago, it was thought that the body stayed healthy by maintaining the balance of the four humours within the body - black bile, yellow bile, blood and phlegm. Now, if you went out into the winter’s cold and took in “great gulps ” of cold air, then this would more than likely have irritated the lungs thus producing more phlegm - in other words they’d develop very productive coughs - and if it that then turned into a pneumonia then you would literally catch your death ..because ... of cold!
But can we catch infections out of the air, and if so what sort: and if we do, then how do we reduce the risk of catching such infections?
When we think of air-born infections, we have to consider three main groups of infective agents: Viruses, Bacteria and Funguses.
When considering spread, viruses come in two major groups: those with a fatty coating and which includes most respiratory viruses, such as influenza and parainfluenza viruses: the febrile rash infections caused by measles, rubella, varicella zoster virus or as it is better known - chicken pox: and finally the coronaviruses which cause severe acute respiratory distress syndrome - or SARS. Those without fatty coatings would include the common cold viruses - the adeno, and rhinoviruses - and the now almost eradicated polio virus. This has importance when considering reducing the spread of these viruses because the fatty coated viruses will survive longer at lower relative humidities - in other words drier air - and the ones without the fatty coating will tend to survive longer in higher relative humidities.
These viruses do not exist in the wild and need a human vector in order to spread. However, they can be spread by the so called aerosol effect when infected people cough and sneeze in confined areas such as on public transport, or in schools, shopping centres and even outdoor markets - indeed, wherever people crowd together.
Generally, as the temperature rises, virus survival decreases. Maintaining temperatures above 60°C for more than 60 min is generally sufficient to inactivate most viruses, they will survive longer if they have a moist covering of organic material such as blood, faeces, mucous or saliva to protect them- and most air born viruses will have a covering of salvia or mucous.
And the thing with viruses is that they don’t just cause infections, in fact it’s been estimated that only half of those infected actually go on to develop an illness, but these viral particles can also trigger an immune response leading to an attack of asthma in those who are susceptible.
Bacteria are another, much larger type of organism that can be spread through the air, although most problems caused by these organisms will be a result of infections acquired indoors. The terrible consequences from aerosolized bacterial infections are generally only seen on news broadcasts when biological weapons of mass destruction are talked about: as these are exactly what they say they are - the use of deadly bacteria, sprayed into the atmosphere to kill the maximum number of people with an invisible weapon: an evil practice that must be condemned by all civilized peoples.
Then there are the funghi. The two types of organisms that we have discussed so far nearly always require a human vector to spread the disease, and they mostly cause problems because they happen indoors. But funghi are a natural part of the outdoors and need air currents to spread their spores as a natural part of their life-cycle. The thing with funghi is that they spore on a seasonal basis and don’t get into our living areas unless we actually leave the windows open. This is particularly important for those who are taking medication to suppress their immunity - such as people on cancer treatment or who are taking Steroids for various immune based conditions. It is also the reason why hospitals don’t have windows that open, as those who have a critical illness do not need the added burden of being challenged by a Crytococcus or Aspergillus fungus which can both cause potentially life-threatening illnesses when blown into wards.
So what conclusions can we draw from all of this? Firstly, that although we think the air is devoid of organisms - it isn’t - and in places where crowds gather, both viruses and bacteria can be spread from person to person by aerosol spread. And the way we overcome this is by annual vaccination against the Flu which is 60% effective, and the more of the population that gets vaccinated, the better chances we have of stopping an epidemic or pandemic. But vaccination only covers 3 viruses and has no effect over colds or other viral infections, so protect yourself by giving "Sneezers and Coughers" a wide berth - about 4 meters should be OK, and remember that infectious droplets land on surfaces that you touch too, so avoid touching your face before you have time to effectively wash your hands or clean them with an alcohol wash. And for those who take medications to suppress their natural immunity, then they need to be extra vigilant at all times when these organisms are more likely to be in the air.
But as well as causing infections, these organisms can also trigger asthmatic attacks when the aerosol particle or fungal spore is inhaled - so at the times of year when viruses are common or fungi are sporing, then asthma sufferers should be more conscious of protecting their airways and preventing an asthmatic attack.
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