For every patient who has the classic sniffling, sneezing signs of a rhinovirus infection, there are 4 asymptomatic individuals who are infected, suggests a study presented today at the American Society for Microbiology meeting in San Francisco.
Researchers from McMaster University in Canada recruited 545 McMaster University undergraduates to participate in a clinical study of methods to prevent rhinovirus and other respiratory infections. During September and October of the 2010 and 2011 respiratory virus seasons, the students were asked to swab their noses weekly when they had no cold symptoms and to report any symptoms of a respiratory virus. When participants reported cold symptoms, they were asked to swab daily for 7 days.
During the study period, 167 symptomatic respiratory illnesses were reported, and in 54% of these cases, researchers detected rhinovirus in the nasal swab samples using a polymerase chain reaction assay. They also tested a random sample of 10% of the weekly swabs taken by asymptomatic individuals and found 35 infections, which corresponds to an infection rate of about 8.75% per week among asymptomatic individuals. Asymptomatic individuals shed the virus for up to 2 weeks and could potentially infect others.
“The virus particles can be spread by aerosols or direct contact with an asymptomatic individual,” said lead author Andrea Granados, a graduate student. “There is no treatment for the common cold; therefore, frequent hand washing is important to prevent the spread of the common cold, particularly in the fall.”