The prevention and treatment of viral respiratory disorders
A briefing from the Board of Science
September 2007
Spread of infection
Despite the considerable amount of research that has been conducted into tracking how the viruses that cause respiratory disorders, such as influenza and the common cold, are spread, it is still not fully understood. It is known, however, that millions of virus particles can be shed by those who are infected, via the mucus they produce, and that the home is a significant site for the spread of infection. [see reference 52] Direct contact is the most common cause of the spread of infection.
There is evidence that transmission of the viruses that cause the common cold and influenza occurs by a number of processes including:
- direct contact – where viruses are spread by direct body-to-body contact, for example shaking hands
- indirect contact – where viruses are spread via contact with an intermediate object, this could be surfaces, clothing, utensils, money etc.
- droplet transmission – where contagious material, spread over short distances by droplets and aerosols produced by coughing and sneezing, comes into contact with another person’s eyes, nose or mouth
- airborne transmission – where viruses travel on dust particles or small respiratory droplets such as those produced when people sneeze, cough, laugh or exhale. These can be suspended in the air and travel with air currents over considerable distances. With airborne transmission, direct contact with someone who is infected is not necessary for viral spread. [see reference 16]
The East of England Strategic Health Authority (SHA) recently carried out a survey which found that 44 per cent of people in the East of England believe that someone coughing or sneezing without covering their mouth is the habit which annoyed them most. Yet despite this, only 21 per cent were found to always carry a tissue, and only 52 per cent throw away tissues after using them once. The survey also showed that 10 per cent of people never wash their hands after covering their mouth or nose to sneeze. [see reference 56]
Many believe that the common cold, influenza and other infections such as tuberculosis (TB) can be spread by spitting. A publication from the National Health Service (NHS), Tuberculosis: TB is on the increase – make sure you know the facts, [see reference 57] states that this is not the case. A leaflet from the WHO and UNICEF however highlights ‘not spitting’ as a key behavioural intervention for reducing risk of transmission during pandemic influenza. [see reference 33] While it may remain unproven, the spread of infection by spitting is a possibility given that virus particles will be present in the saliva of infected individuals.
A case study of school children in America showed that absences due to illness decreased 20 per cent in those who used hand sanitisers at specific points during the day, in addition to their normal hand cleaning habits (see figure 2). [see reference 58]
Source: Hammond B, Yusuf A, Fendler E et al (2000) 'Effect of hand sanitizer use on elementary school absenteeism'. American Journal of Infection Control 28: 340-6.
Avoiding the spread of infection
Due to the large number of viruses that cause respiratory disorders such as the common cold, and in particular the fact that many of these are able to mutate rapidly, no effective vaccine has yet been developed to protect against all of the viruses that cause such respiratory disorders. That said, there are many precautions that can be taken to reduce spread:
- hand washing – a recent study showed that simple handwashing with soap can significantly reduce the number of pneumonia-related infections in children under the age of five. [see reference 59] Washing is especially important before and after food preparation and after using the toilet. Leeds teaching hospitals produce a guide to promote and sustain improved compliance to the practice of hand hygiene [see reference 60]
- alcohol sanitisers – these can be used as a supplement or alternative to hand washing with soap and water. Sanitisers containing alcohol are more effective at killing bacteria than soaps and do not dry out hands as much [see reference 61]
- avoid touching eyes, nose and mouth – any viral material which may have been transmitted to hands will easily spread to these tissues where they can replicate easily [see reference 62]
- clean surfaces thoroughly – due to the long survival times of viruses, especially on non-porous surfaces (which can be up to two days or more), it is important to clean surfaces in order to reduce the risk of infection especially where the concentration of infectious agents is highest. Cleaning with soap and water is usually adequate to remove germs. If, however, someone has influenza it is important to disinfect surfaces for extra protection. Disinfection should be carried out using a simple chlorine bleach solution on surfaces such as door knobs, light switches, telephones, etc. It is also important to use disposable towels which are disposed of at once or cloth towels which are laundered immediately, in order to reduce the risk of spread [see reference 63]
- use disposable (paper) tissues – due to the long survival times of viruses, even on porous materials (up to 12 hours), the use of disposable tissues allows for easy disposal of potentialy infectious materials [see reference 56]
- avoid sharing glasses or utensils – this reduces the risk of indirect transmission of viruses, and is particularly important where someone else is known to be infected
- avoid contact where possible – this reduces the chance of transmission, and is especially important where someone is known to be infected [see reference 64]
- take antibiotics sensibly – antibiotics kill or damage bacteria not viruses, and are not effective against the common cold and influenza. Improper use of these drugs can give rise to resistant strains of bacteria. For more information see Healthcare associated infections (BMA, 2006) [see reference 65] and Evidence-based prescribing (BMA, 2007) [see reference 66]
- get vaccinated – vaccination offers a cost-effective first line of defence against influenza, and depending on the virus in circulation, vaccination is about 70 per cent effective (30 to 90%).13 It is reported that the best time to get vaccinated (in the UK) is between September and November. [see reference 67] (For more information see the section on Vaccination and treatment).