Via his blog Virology Down Under, Dr. Ian Mackay discusses a subject on everyone's mind since the identification of asymptomatic MERS cases. Excerpt:
Recent findings from Tricco and colleagues of a real and sizable "off-target" effect due to mismatched vaccines (reduction in influenza virus infections by influenza viruses that were not included in your most recent injected or sprayed vaccine) is a great additional incentive to get vaccinated, even if you are outside the at-risk groups. As is the recent Illinois-based study of weekly viral and bacterial incidence data from 1989-2009 (with a gap in between; total of 926 weeks in total), concluding that influenza infection resulted in a 100-fold increase in susceptibility to pneumococcal (Streptococcus pneumoniae in this case) pneumonia.
In light of recent findings of asymptomatic MERS-CoV people, it is important to understand what a PCR positive means for a patient without signs or symptoms of disease. Whether that situation will last for the course of their infection (truly asymptomatic) or symptoms will develop after the sampling time (pre-symptomatic) is another variable to consider.
In a 2009 review of published studies by Patrozou and colleagues, asymptomatic or pre-symptomatic influenza cases were not been found to be a major contributor to virus transmission. The authors also concluded that there was scant evidence of a role and that more studies were needed. Is this finding applicable to all respiratory viruses? If so, can we extrapolate these data for influenza virus to MERS-CoV cases for instance?
