Respiratory syncytial virus and rhinovirus cause more trips to the doctors office fever than other identified viral respiratory pathogens in children attending day care, according to recent research.
[PCR] has allowed us to better define which viruses cause the most impact on children in the age range studied, said Mary P. Fairchok, MD, of the Madigan Army Medical Center in Tacoma, Wash., and Seattle Childrens Hospital and Regional Medical Center.
Fairchok and colleagues conducted a prospective study in which real-time PCR was used to determine the epidemiology and relative importance of the viruses found among children in two particular day care centers. Their results were presented at the 45th Annual Meeting of the Infectious Diseases Society of America held in San Diego.
Virus detection through PCR
Fairchok and colleagues enrolled 101 children (mean age, 11 months; range, 1.5 to 25 months) from two day care centers.
Between February 2006 and March 2007, the researchers collected nasal swabs whenever the children had respiratory infections. They then performed real-time PCR on the swabs to detect RSV; human metapneumovirus; influenza A and B; parainfluenza viruses 1, 2, 3 and 4; adenovirus; human coronavirus subtypes 229E, HKU1, NL63 and OC43; and rhinovirus.
The childrens caregivers were asked to complete symptom diaries for each of the illnesses as well.
The mean annual incidence of respiratory tract infections was 6.2 per child, and children had respiratory tract infection symptoms for an average of 20% of the time, according to the researchers.
We found at least one virus in 61.5% of respiratory tract infections, the researchers wrote in the abstract. Coinfections with multiple viruses were common (23% of respiratory tract infections), with rhinovirus, coronavirus and adenovirus [as] the most common co-pathogens.
Real-time PCR detected only six cases of influenza A and B, and seven out of 30 parainfluenza infections detected were type 4.
The two viruses that had the biggest impact were rhinovirus and RSV, Fairchok said. Some of the more newly identified viruses, such as new human coronavirus subtypes and human metapneumovirus, did not seem to cause as much significant illness as measured by things like fever, visits to a health care provider and absence from day care.
Although RSV was not the most common virus identified, the researchers found that it caused the most severe illness and resulted in the most amount of work missed by parents per infection (3.7 days; P<.02). Rhinovirus was the most common virus detected through PCR and resulted in the most clinic visits and reports of fever.
Physicians can tell their parents with children in day care to expect them to have six to 10 respiratory infections per year most occurring in the second portion of the first year of life, Fairchok said.
What this means
She added that, based on these results, children in this population can be expected to miss about a day of day care per infection.
According to Fairchok, the predominance of RSV as a cause of significant disease in this population further emphasizes previous information that day care attendance is a risk factor for RSV, and that this should be taken into account when determining the need for prophylaxis.
One thing the researchers found surprising in this study was that, despite the effectiveness of PCR in defining the effect of respiratory viruses within the day care setting, they were still unable to identify a pathogen in about 40% of the illness events.
There are several explanations for this, according to Fairchok.
Possibilities include that there are other as yet discovered viruses causing disease; that some of the illness events were not infections, but perhaps allergic rhinitis; and that bacterial pathogens could have caused some of the illnesses, Fairchok said.
The researchers were also surprised to find that rhinovirus was as important as RSV in this population in terms of having a large effect on cases of fever, number of illnesses and number of health care visits.
Rhinovirus has typically been felt to be a cause of more mild illness than other respiratory viruses, although evidence is mounting that it may play a bigger role in serious respiratory infections than previously realized, Fairchok said.
For more information:
- Fairchok MP. Prospective study of viral respiratory tract infections in young children attending day care. #672. Presented at: the 45th Annual Meeting of IDSA; Oct. 4-7, 2007; San Diego.