It’s the season of respiratory illnesses and with COVID-19, RSV, and flu abound, it’s hard to make it to spring unscathed. Stories in the news talk about the recent rise in respiratory virus activity over the holidays (here, here, and here) and how respiratory symptoms just won’t seem to subside. A winter full of respiratory symptoms might be particularly true if you have a kid in school or daycare. When little Storm started daycare, we knew he’d be getting sick himself and bringing home the viruses behind these illnesses.
Three weeks after the start of daycare, Storm brought home a stomach bug. A few weeks after that, COVID-19. Then we couldn’t tell when one illness subsided and when the next began. The rate of illnesses has got to slow down at some point right? Naturally, as a microbiologist, I decided to scour the scientific literature looking for answers. Here’s what I found.
When will the sicknesses end? A tired parent asks
The first study I came across was from 2017.
This study examines the exact question I was asking: when will my child stop getting sick all the time after starting daycare? This study had parents record respiratory symptoms daily in the six months prior to starting daycare through nine months after starting daycare (talk about commitment!). They compared data from the kids who stayed home (350 kids), kids who attend a small daycare with less than five children (245 kids), and kids who attend a large daycare (299 kids). All kids were less than two years old throughout the study.
From the reports, they found that respiratory symptoms peaked two months after starting daycare (averaging 8 days with respiratory symptoms per month for kids in a small daycare and 11 days/month for kids in a large daycare, compared to 4 days/month for kids at home). While the data shows a sharp rise in the number of days per month sick once starting daycare, the data also shows a decrease in the number of days sick per month within nine months.
Image: A comparison of sick days/month between kids at home and at daycare. We’ve just finished our sixth month in our household. Crossing our fingers as this coincides with winter illnesses! Source: Schez-Navupalo et al., 2017.
We are about six months into our daycare journey and while we are still seeing illnesses crop up regularly (and hello winter!), we’re remaining hopeful that in a few months, illnesses will be less frequent.
Sick now or later: Children get the same number of illnesses by age eight
In the throes of new-to-daycare illnesses, you may be wondering whether this illness phase could be avoided altogether. Unfortunately, no.
An eight year study tracked children’s respiratory symptoms from when they were 5 months old through 8 years old. The study collected “maternal reports” of symptoms of respiratory illness, ear infection, or gastrointestinal infection (yes, I’m annoyed the study seemed to only ask mothers for reports…).
They found that kids (<2.5 years old) who attended daycares with more than 6 children had higher rates of respiratory infections and ear infections during that time, but had fewer of these infections during elementary school years. These effects were not seen for children who attended group child care after 2.5 years of age or for those who attended smaller childcare groups.
One thing they did note: regardless of whether children attended daycare or not, the children in the study all end up getting the same number of illnesses by age 8.
Asymptomatic carriers? Beyond COVID-19
Through COVID-19, we’ve all become familiar with the concept that an individual can carry a respiratory pathogen but have no symptoms of disease. And for those individuals without symptoms, you’d never know if they carry the pathogen behind the disease unless you tested them. This is what I was wondering when Storm kept getting new illnesses right at the start of daycare when none of the other kids were visibly sick: just how many of us are asymptomatic carriers of respiratory pathogens?
A study published in 2016 evaluated 161 children in daycares during autumn and winter months by swabbing their noses and using PCR to test for 19 respiratory pathogens including RSV, influenza, rhinoviruses, coronaviruses, adenoviruses, Bordetella pertussis, and Mycoplasma pneumoniae.
They found that 43% of all swabs were positive for 1 of the 13 viruses they tested for – that’s almost half of kids tested carrying the nucleic acids of at least one respiratory pathogen. But what fraction of these swabs came from children with respiratory symptoms vs. those without symptoms? Viral nucleic acids were identified in 70% of kids with signs of respiratory infections, 41% of kids with mild symptoms, and 30% of kids without any respiratory symptoms. This may seem like a large percentage, but there’s a caveat to the study: detection of viral nucleic acids doesn’t necessarily mean an active infection.
This study was done before COVID-19 so I was interested in seeing similar data for COVID-19. A study published in JAMA Network Open this year found that SARS-CoV-2 transmission rates were around 2-3% within daycare centers. The study period was from May 2021 to March 2022, when vaccines were available to adults but not to children under 5 and included the Omicron wave, so the numbers might be a bit different now with more vaccinations and different strains circulating.
TL;DR: A microbiologist parent’s thoughts on these studies
I surveyed only a few of the studies out there on this subject and I’m sure there are a lot more out there. I found it reassuring that the first study found that the number of sick days/month decreased within nine months of starting daycare and that kids get around the same number of illnesses by eight years old – it’s just a question of whether they get these illnesses at a younger age or later.
