COVID-19 transmission with or without symptoms
Being sick with COVID-19 means having symptoms and then getting tested, isolating and adhering to other safety measures. But when a COVID-19 infection occurs without symptoms, there’s often no testing, and yet the person can still transmit the virus. Notably, the level of SARS-CoV-2 virus and the time it stays in the upper respiratory tract are the same in an infected person with or without symptoms.
Asymptomatic spreading of COVID-19 is one of the reasons that it’s tough to contain the pandemic, because if you don’t know you’re infected, you can unintentionally infect others. Inadvertent spreading can be the case with children, because they are mainly asymptomatic or only mildly ill. So we need to figure out whether it’s about the virus or close physical contact.
Children do spread COVID-19
Early on during the pandemic, researchers from Wuhan, China, published a study showing that COVID-19 in children was a link in the transmission chain. They evaluated over 27,000 households and demonstrated that COVID-19 positive children infected other family members more frequently than adults. They also found that infants were more likely to be infected in the household with COVID-19 than children between 2 and 5.A few months later, another study concluded that children were not to blame for spreading COVID-19 (DOI: https://doi.org/10.1542/peds.2020-004879).
Since then, there have been other contradictory studies. However, we still don’t know whether they’re unwittingly spreading the virus and whether a child’s age influences transmission. But recently, a Canadian research team did a population study to find whether children spread disease in their households, and if so, which age group most likely transmits the virus.
The researchers set out to identify the first member (primary case) in a household under 18 who was COVID-19 positive and then asked whether anyone else became positive (secondary case) within the following two weeks. From June to December 2020, they studied over 6000 households and found that children between 0 to 3 years were most likely to transmit the virus to other household members, followed by children aged 4 to 8 years and 9 to 13 years. About 12% of the primary cases were children under 3, and almost 30% of households had at least one other secondary case. The results are significant. Still, the study has limitations that include a chance that transmission (the secondary case) occurred outside and not within the household and that the first case was not identified, because the child was asymptomatic and not tested for COVID-19.
Still, while the study shows that infected young children spread disease more than older household members, it’s unclear why. One possible explanation is that if they’re asymptomatic, no one suspects that they have COVID-19 and don’t test or isolate them. Another possibility is that young children may have higher viral loads or higher viral shedding than children and adults. However, this is rather unlikely because viral loads and shedding appear to be the same for children and adults and don’t seem to correlate directly with being more contagious. The most likely reason is that certain behaviors may explain why children under 3 are better at spreading the virus; infants and toddlers require more close physical contact and care, they cough and sneeze with open mouths, put things in their mouths and then touch and potentially infect surfaces and people. It’s also difficult to isolate them when they’re sick. Understanding which factors most influence spread is essential because it might help reduce household viral transmission.
Minimize the risk of secondary spread within your household
Children under 12 are not yet eligible for a COVID-19 vaccine and remain among the largest unvaccinated population. Unvaccinated plus asymptomatic equals high risk of these young children spreading the virus. Until we have more studies about how significant this type of household spread is, we need to minimize the risk of secondary spread within the household.
But it’s not easy to isolate infants and toddlers, because they need close physical contact. So, here are some tips that might help:
- Everyone in the household over 12 should be vaccinated and get regular COVID-19 tests so small children can be properly taken care of
- Vulnerable adults should wear masks when in close contact with infants and young children
- Children over 2 could also wear a face mask when near vulnerable siblings and adults in the household
- Have young kids COVID-19 tested if they’ve been in contact with infected people or are positive
- Try to isolate sick children from other siblings and vulnerable adults, if possible
- Caregivers should wear face masks when caring for a sick or COVID-19 positive child
- Wash hands after handling children
- Throw away tissues and other potentially infected materials
- Clean frequently touched contaminated surfaces
- Teach toddlers and older children how and when to wash their hands
- Practice physical distancing at school and with other children, if possible
- Be sure that there is good ventilation indoors
- Avoid large crowds and public places with young children
Remember, if infants and toddlers are transmitting the virus, they could be extending the pandemic. With the number of children with COVID-19 continuing to rise, household transmission by children will also grow. Therefore, we need to be aware of the risk of children spreading disease, minimize it, and move quickly towards vaccinating young children as soon as the clinical trials demonstrate effectiveness and safety.