September 24, 2009

Measures To Reduce Spread Of Viruses

Taking basic steps such as proper hand-washing, wearing masks and quarantining infected people can help prevent the spread of flu and other respiratory viruses, according to a new study published on Wednesday.

Doctors led by Tom Jefferson, a professor in the Acute Respiratory Infections Group at the Cochrane Collaboration in Rome, reviewed 59 published trials on protective measures against pathogens such as the common cold virus, the Severe Acute Respiratory Syndrome (SARS) virus and the influenza virus.  The current H1N1 "swine flu" pandemic strain was not included.

Although the trials used broad formats, they all examined the number of people who were infected when protective measures were undertaken compared to the number who became ill without such protection.  Vaccines and antiviral treatments were not included in the studies.

In hospital environments, routine hand-washing more than 10 times a day and the use of masks, gloves and surgical gowns were each effective against spreading respiratory virus.  These steps were particularly useful when combined, the analysis found.  Home hygiene measures, in particular those targeted at younger children, also helped prevent transmission.

"Perhaps this is because younger children are least capable of hygienic behavior and have longer-lived infections and greater social contact, thereby acting as portals of infection into the household," wrote the doctors in a report about their analysis.

Two studies found that isolating potentially infected individuals was also effective in preventing infections.

Interestingly, the review uncovered only limited evidence that "N95" surgical masks perform any better than conventional, simple facemasks.  The N95 masks, which are less comfortable and more expensive, can also cause skin irritation, the studies found.

"We found limited evidence of the superior effectiveness of barrier devices to droplets such as the N95 masks over simple surgical masks. N95 masks are respirators with 95% filtration capability against non-oily particulate aerosols. Although they are more expensive and uncomfortable (especially if worn for long periods) than simple surgical masks, they may be useful in high-risk situations," the doctors wrote.

The team acknowledged that it was at times difficult to reach a generalized conclusion given the diversity of the studies and vagueness of the data.  Nevertheless, some simple measures have high potential for reducing infections during a viral respiratory epidemic.

"Vaccines work best in those who are universally considered least to need them -- namely, healthy adults. Antivirals may be harmful and their benefits depend on the identification of the agent."

"But physical interventions are effective, safe, flexible, universally applicable and relatively cheap."

"Based on the findings of this review, we recommend that hand washing programs should be implemented nationwide, their effectiveness monitored, and their cost effectiveness evaluated," the authors wrote.

"In situations of high risk of transmission, barrier measures should be implemented such as wearing gloves, gowns, and masks with a filtration apparatus, and isolation of likely cases. Most effort should be concentrated on reducing transmission from young children through regular education at school on hygiene. In addition, society should invest in more comfortable and better designed face masks and barrier apparatus, which would increase compliance with their use," they concluded.

The analysis was published online in the British Medical Journal. 


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