New research shows that families with teenage children were three times more likely to get Covid (odds of spread , 18%) than families with children under ten (5%). It appears that it’s more dangerous to live with teens than to live with adults (12%). It may be that teens are more likely to be asymptomatic which means people don’t realize they need to isolate from them.
The question of opening primary schools is potentially very different to high schools. Quite possibly puberty affects immune systems in ways that make teens effectively young adults.
The results also showed up something unexpected, however. When index patients were categorised by age (0–9, 10–19, 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and >80 years), households with older children (index patients of 10–19 years) had the highest rate of infection spread to household contacts, with 18.6 percent of household contacts later showing the infection.
By contrast, young children (index patients 0–9 years of age) seemed to confer the least amount of spread of the virus, with just 5.3 percent of household contacts contracting the infection, which is less than half of the 11.8 percent average of all age groups (most of whom represent adults).
The study in South Korea involved nearly 60,000 contacts of 5,700 Covid patients. The spread was six times more likely at home than outside home with 12% of household contacts catching the disease at home, but only 2% of contacts outside home catching it. Since this is Korea it’s likely that people wore masks outside the home. The researchers say “the role of masking within the home, especially if any family members are at high risk, needs to be studied.” For the record — schools were largely closed in South Korea during the test period. They remained open for essential workers children and were limited to very small class sizes. So the study doesn’t necessarily tell us much about the spread at school.
Donald Trump has at least conceded that schools in hot spots should delay reopening. The spread of coronavirus hurts his campaign and helps Democrats in so many ways. Getting on top of this spread should surely be a top priority.
UPDATE: Ponder how unusual this epidemiology is:
Traditionally the under fives are the wildly dominant spreaders of any disease. Hands on everything. This is very different from the flu. While the under fives are short, and therefore “breathing lower in altitude” we pick them up and carry them and face to face contact is common. Not so with 12 year olds.
Teenagers (older ones) are out and about and may pick up the disease through careless behaviour. But it may be that teens are larger asymptomatic shedders of virus, and for some reason the youngest children aren’t. Perhaps the youngest wipe this virus out fast with innate immunity and therefore are not big shedders for long. In any case, the implications are that primary schools could be reopened more easily — which will help parents go to work. But teens could learn from home. It might be the lowest impact way to slow the virus with the smallest impact.
This is different.
Young June Park et al (2020) Contact Tracing during Coronavirus Disease Outbreak, South Korea, Emerging Infectious Diseases. Volume 26, Number 10—October 2020, https://doi.org/10.3201/eid2610.201315