A new study by scientists at the University of Utah reveals that big families have viral infections for 87% of the year.
The study is one of the first long-term studies to use modern diagnostics to track the presence of common viruses in kids and their families. The year-long research project kept track of viruses like influenza, parainfluenza and rhinovirus — the cause of the common cold. The team found that people living in childless houses are infected with viruses just 3-4 weeks per year. Meanwhile, adding a single child to the household bumps that figure up to 18 weeks—which is 35 percent of the year—and a second to 29 weeks. By the time a family has six children, there’s a virus in the household for up to 45 weeks per year.
The correlation is clear, but the cause is harder to ascertain. The researchers found that young children may be to blame: those under five had viruses in their nasal mucus for 50% of the year, and when infected were 1.5 times more likely to display symptoms, such as coughing that would spread the infection. The study also shows however that only half of people who tested positive for viral infections actually displayed symptoms like coughing and fever .
The results are published in Clinical Infectious Diseases.