House Too Often a Home for COVID-19 Infection

While infection prevention efforts mostly focus on healthcare transmission and prevention strategies, we know that often, the highest risk and lowest awareness can be outside the healthcare facility. Healthcare workers are vigilant with their personal protective equipment (PPE), hand hygiene, and disinfection efforts in the hospital as that is where we manage infectious and ill patients. Too often, healthcare professionals think that when they leave the hospital, the risk evaporates and sadly, that’s where we see risk awareness falter. Similar to outbreaks related to socializing in the breakrooms, it’s often challenging to discuss risk outside the hospital for those who spend their days in one.

Household contacts are one piece to this complexity and can be challenging to explain in terms of quarantine. For those unable to isolate within their household after a diagnosis of coronavirus disease 2019 (COVID-19), the quarantine period for those within the household doesn’t truly begin until the person is no longer considered contagious. For some, this means 10 days of isolation and then 14 days of quarantine for household contacts, which actually means 24 days as close contacts in the household still need to stay home during the first isolation period.

How risky can households be, though? A new study in the Center for Disease Control and Prevention (CDC)’s Morbidity and Mortality Weekly Report (MMWR) assessed household contacts and transmission across dozens of contacts through a case-ascertained study in Nashville, Tennessee and Marshfield, Wisconsin from April to September of this year.

Saskia v. Popescu, PhD, MPH, MA, CIC

Following enrollment, those index patients and their household members were trained to complete symptom diaries and obtain self-collected specimens daily for 14 days. There were 101 households (e.g. 101 index cases) and 191 household contacts, with a median index patient age of 32 years. The research team found that the 191 contacts of 101 index patients had no symptoms on the day the index case’s illness began, but of those 191 close contacts, 102 had the virus detected during a follow-up. The secondary infection attack rate was 53%.

The researchers noted that “among fourteen households in which the index patient was aged <18 years, the secondary infection rate from index patients aged <12 years was 53% (95% CI = 31%–74%) and from index patients aged 12–17 years was 38% (95% CI = 23%–56%). Approximately 75% of secondary infections were identified within 5 days of the index patient’s illness onset, and substantial transmission occurred whether the index patient was an adult or a child.”

Interestingly, in 102 of the household members, the detection of SARS-CoV-2 occurred via PCR during the first 7 days of follow-up. Forty percent of those infected household members did report symptoms at the time of the first positive test. When the 7-day follow up occurred, 67% of those infected household members reported symptoms, which began around day 4.

It’s also important to note that not only was the median age of the index patient quite young, but of the household contacts who developed COVID-19, the secondary infection rate was 53% for those under 12. Even more interesting, of the 101 index patients, 5 were less than the age of 12 and 9 were between the ages of 12-17, meaning that nearly 14% of all the index patients were under the age of 18. Ultimately, this not only teaches us about the role of household transmission, but that children are still susceptible to not only the disease, but also act as a transmission source. Ensuring people are able to isolate appropriately when infection occurs and limit household interactions will be important for reducing the overall disease burden.