Thursday, January 21, 2010

Study: Effectiveness of NPIs Against ILI's



# 4274



Regular visitors to this blog blessed with long memories will probably recognize the  University of Michigan study below as one we looked at nearly 15 months ago in a blog entitled Study: NPI's Can Help Prevent Spread Of Flu-Like Illnesses.


NPIs are non-pharmaceutical interventions . . . like masks, gloves, hand washing, social distancing, etc.


At that time some of the data had been collected and analyzed, and the early indications were promising.   In fact, there was a short (4:20) video describing the study linked from that first blog, which you can view by clicking the image below.






The press release from the IDSA  follows, with links to the abstract and a few excerpts.


As you read this information, a few points to bear in mind:


  • this study was conducted prior to the emergence of the novel H1N1 virus
  • ILIs `influenza-like symptoms’ may be caused by viruses other than influenza A.
  • Combined hand washing and facemask use lowered risks 35% to 51% over the control group
  • No comparisons between the relative effectiveness of facemasks and respirators were studied.



Contact: John Heys
Infectious Diseases Society of America


Study finds face masks and hand hygiene can help limit influenza's spread

Ordinary face masks and hand hygiene can effectively reduce the transmission of influenza-like illness during flu season. The finding comes from a new study, now available online, published in the Feb. 15 issue of the Journal of Infectious Diseases. In an influenza pandemic, vaccination may not be initially available, and antiviral prescribing may be limited, which is why scientists need to understand how effective other measures are in preventing influenza.


For the study, researchers from the University of Michigan School of Public Health, led by Allison E. Aiello, PhD, recruited more than 1,400 college students living in university residence halls during the 2006-2007 influenza season. Participants were assigned to one of three groups: those who wore face masks, those who wore masks and used alcohol-based hand sanitizer, or a control group who received no intervention. Students were monitored for influenza-like symptoms for six weeks. All participants viewed a basic hand hygiene instructional video. Subjects in the hand hygiene and mask group were given an alcohol-based hand sanitizer and written instructions regarding proper face mask and hand sanitizer use. Those in the mask group received written instructions on face mask use only. The students began using the measures just after laboratory confirmation of influenza on the University of Michigan campus had been made.


The investigators observed significant reductions in the incidence of influenza-like symptoms starting after three weeks in the hand sanitizer/mask group and in the mask group compared with the control group. In the hand sanitizer/mask group, Dr. Aiello and researchers found a reduction of influenza-like symptoms ranging from 35 to 51 percent when compared with the control group. The incidence of symptoms between the hand sanitizer/mask group and the mask-only group were not statistically different, suggesting that the use of hand sanitizer did not substantially contribute to reducing symptoms.


(Continue . . . )



The Journal of Infectious Diseases 2010;201:000–000


DOI: 10.1086/650396


Mask Use, Hand Hygiene, and Seasonal Influenza‐Like Illness among Young Adults: A Randomized Intervention Trial

Allison E. Aiello, Genevra F. Murray, Vanessa Perez, Rebecca M. Coulborn, Brian M. Davis, Monica Uddin, David K. Shay, Stephen H. Waterman, and Arnold S. Monto


Methods. A randomized intervention trial involving 1437 young adults living in university residence halls during the 2006–2007 influenza season was designed. Residence halls were randomly assigned to 1 of 3 groups—face mask use, face masks with hand hygiene, or control— for 6 weeks. Generalized models estimated rate ratios for clinically diagnosed or survey‐reported ILI weekly and cumulatively.


Results. We observed significant reductions in ILI during weeks 4–6 in the mask and hand hygiene group, compared with the control group, ranging from 35% (confidence interval [CI], 9%–53%) to 51% (CI, 13%–73%), after adjusting for vaccination and other covariates. Face mask use alone showed a similar reduction in ILI compared with the control group, but adjusted estimates were not statistically significant. Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively.


Conclusions. These findings suggest that face masks and hand hygiene may reduce respiratory illnesses in shared living settings and mitigate the impact of the influenza A(H1N1) pandemic.


Although this study did not directly study the effectiveness of hand washing alone, the implication here is that alcohol sanitizers and hand washing alone may not be as protective as has been hoped in the past.


Still, hand washing is always a good idea.  We know it reduces other, equally serious, illnesses.  And it may well decrease the spread of some types of respiratory illnesses. 


Its efficacy in the reduction of influenza, however, remains unclear.