What’s common about a cold? Well, maybe more than previously thought. New research has suggested that people may be infected with rhinovirus, the most common virus causing respiratory tract infections, without knowing it. This is relevant for individuals in close quarters such as families, schools and workplaces.
University students living and studying in close quarters provide an ideal group to study. Over five hundred university students were studied for 8 weeks during the cold and flu seasons of two consecutive years. Nasal swabs were collected once weekly even if the students were feeling well. If the student reported cold like symptoms, nasal swabs were taken daily for one week. The nasal swabs were tested using DNA-based polymerase chain reaction to identify the type of virus present, and in over half the ill students, rhinovirus was detected.
So, researchers knew that many of the students with colds were infected with rhinovirus. However the scientists wanted to investigate how many of the students without colds also had the virus. In order to do this, 10% of the nasal swabs from healthy students were randomly selected for testing. Based on the results, researchers estimate that as many as 60.5% of the asymptomatic student population was infected at some time with rhinovirus over the eight weekly study period.
Another interesting finding from these results was that the students who tested positive for the presence of the virus but were asymptomatic had significantly lower viral load – which means they had less of the virus in their nasal sample. This probably accounts for the lack of symptoms, although more research is needed to establish if this is actually the case.
Similar results were found in family based study. Parents of young children presenting with a cold were often found to be infected with rhinovirus without experiencing cold symptoms. Not surprisingly rhinoviruses are transmitted efficiently between young children in the same family, and then onto older siblings and parents.
Researchers found there can be several different rhinoviruses circulating within one family at the same time, causing overlapping symptomatic periods. Possibly parents do not develop cold symptoms due to protection from acquired immunity. The authors of this study propose that actual cold symptoms are necessary for the cold to be passed on. This seems to reflect what many parents of young children, already know – one family member with a cold starts a domino effect of sick children.
There is no cure for the common cold, so prevention is the only option. Good hygiene including lots of hand washing, a healthy lifestyle with a diet of fresh wholefoods, exercise and adequate sleep can help to decrease the incidence of the common cold.
References available on request