Tom Miller, senior research fellow at the Department of Medicine, University of Auckland, offers some research results for surviving the winter.
With cases of swine flu already being reported and winter illnesses about to peak it is timely to reiterate the practical measures that can be taken to avoid respiratory infections and related problems.
The contribution of droplet contamination through sneezing and coughing to the spread of coughs, colds and influenza
is widely appreciated. Less well known is the fact that droplet spread is only part of the story.
More often than not, respiratory viruses have been picked up through touch contact with a contaminated surface and transferred by touch contact to a virus promoting surface such as the mouth, eye or nose.
How often have you heard the comment "I can't imagine where this cold came from. I haven't been near anyone with a cold for ages."
Think about it for a moment. Most of us cover our mouth to smother a cough or sneeze and then carry on with the next task ... opening a door, picking up the phone, hanging on to a strap in the bus or shaking hands with the next client.
The school environment, family home, work place, gymnasium, library and other communal areas are all sites of potential contamination and contact with infectious virus.
Hand hygiene continues to be the best and most practical option available to the general public for their protection against infectious diseases acquired through touch contact.
Historically, the first recorded successful intervention in disease transmission by touch contact was carried out by Dr. I. P. Semmelweis in the 1840s. Puerperal or child birth fever is caused by a virulent streptococcus and was common in the mid-nineteenth century among women giving birth in "lying in" hospitals with mortality rates as high as 35 per cent of admissions.
Dr Semmelweis introduced a programme of stringent hand washing in chloride of lime for his staff before patient contact. The mortality rate in his wards quickly fell to less than 1 per cent.
One hundred and fifty years later, research carried out in the Department of Medicine University of Auckland established unequivocally that the degree to which infectious agents are spread and acquired by touch contact is determined by the level of moisture on the hands.
Typically it was shown that up to 70,000 micro-organisms could be transferred to surfaces representing skin, food and utensils by wet hands.
This number was reduced to just a few hundred if the hands were carefully dried before touch contact was made. The results of these experiments have been recognised internationally and effective hand hygiene is now regarded as a two-step process.
Hands must be washed thoroughly and, equally important, dried with considerable care. Thorough washing involves holding the hands under running tap water for at least 20 seconds with purposeful hand rubbing.
Drying is also best carried out in two stages.Our prescription for effective hand drying has been described as the 10/10 method. The first step is to carry out a 10-second dry with a cloth or paper towel to remove the bulk of water on the hands after washing. This is followed by a further 10 seconds drying under a warm air dryer to dissipate the remaining moisture.
It is uncommon to find a warm air dryer adjacent to cloth or paper towels in which case a repeat 10-second dry should be carried out with fresh material.
In situations where a warm air dryer is the only unit available it is important to allow for a 45-second drying time. The bad press often ascribed to warm air dryers is due entirely to the fact that, in practice, they are used for just a fraction of the time needed to achieve dry hands.
The value of observing the 10/10 hand drying protocol, in terms of reducing microbial transmission by touch contact, has been demonstrated recently in a study carried out in an Auckland City child-care centre. Children attending child-care centres suffer from substantially higher rates of infection compared with those cared for in the home.
The illnesses, which include respiratory infections, infectious diarrhoea and ear problems represent a significant burden of ill health for the children and an associated economic cost when working parents take time off to provide home care. This factor is compounded when infectious agents initiate a cycle of illness within the family home.
Items in common use by children in child-care centres provide an ideal reservoir for disease-causing micro-organisms and any reduction in contamination levels would confer considerable heath benefits. The hypothesis was that replacing a child's "usual", unmonitored, hand-hygiene practice with a supervised 10/10 hand-drying protocol would result in a reduction of the number of micro-organisms being transferred to common items by touch contact.
This turned out to be the case and microbial numbers transferred to skin, food and toys by touch contact were reduced by up to 96 per cent when the dual hand-drying system replaced the child's normal routine.
Alcohol-based products are now being heavily promoted as an alternative to hand washing and drying and may well have a place in situations where there is a lack of hand-hygiene facilities. While their activity against influenza viruses has been shown to be satisfactory, other viruses, including the norovirus and rotovirus, require higher concentrations of alcohol than are found in most rubs.
In direct comparative studies, hand washing has been shown to be more effective at removing virus from the hands than alcohol-containing preparations.
The message for getting through the winter free of coughs, colds and influenza is a simple one.
Wash your hands thoroughly and frequently. Dry them carefully using a dual drying technique.
Avoid touch contact with mucosal surfaces above the neck. In the family home and shared dwellings, individuals should have their own towels to avoid back transfer of infectious agents by touch contact with communal linen.
Enjoy your winter.
