Asymptomatic carriers – a threat to the elderly
As our understanding of Covid-19 develops, it has become clear that asymptomatic carriers could be the biggest threat when it comes to containing the virus – most notably in senior living communities, due to the elderly’s high susceptibility to the virus.
Barry Kaganson, chief executive officer of Auria Senior Living – a company that develops, owns and operates senior living communities in South Africa – says: “It is becoming clear that the biggest battle the medical community is facing, when it comes to containing this coronavirus, is in identifying carriers. Previous thinking was that symptom identification was sufficient; however, recent case studies are showing that there is actually far more that can be done.”
A case study released by the United States Centers for Disease Control and Prevention in early April, which focused on a sub-acute nursing facility in King County, Washington, showed that of the 23 residents who tested positive for Covid-19, 13 reported no symptoms initially.
A mid-April study showed that up to one-third of residents in Chelsea, a hot spot in Massachusetts, may have been infected, and only half of them could recall having a single symptom over the previous four weeks. Another small study, of pregnant women in New York City, found that 15 percent tested positive for the virus, and 80 percent of them had no symptoms.
Pre-symptomatic transmission (that is, people passing on the virus before they show any symptoms of Covid-19) has been well documented. The incubation period, which is the time between exposure to the virus (becoming infected) and symptom onset, is on average five to six days; however it can be up to 14 days. During this period, also known as the “pre-symptomatic” period, some infected persons can be contagious. Therefore, transmission from a pre-symptomatic case can occur before symptom onset.
Containment and testing are critical
While most of us have thought that a combination of obvious symptoms and Covid-19 testing are sufficient to identify those who are infected, it is now clear that there is a major risk associated with symptomatic assessment alone. If the disease is contagious even in the absence of obvious symptoms, as it now appears, it means that there is a far higher likelihood of it being spread by unknowing carriers.
Kaganson says that to protect the residents in senior living communities, testing combined with stringent containment measures is vital to protecting the health of the elderly. “Until now, most risk mitigation strategies have been focused around identifying symptomatic people – those with raised body temperatures, coughs, and so on. However, this doesn’t deal with the real risk of asymptomatic transmission,” he says.
He also points out that staff who make use of public transport to come to work run the daily risk of becoming infected. Despite the nationwide five-week lockdown, Auria has been taking steps to mitigate this risk by housing all such staff on site to protect the virtual “bubble of safety” around its senior living communities. However, now that we have entered “Lockdown Level 4”, more industries will have staff returning to work.
A rigorous strategy is needed
“Given that infection rates are due to escalate, we have stepped up our vigilance and will now be doing comprehensive testing among staff before they enter Auria’s senior living communities to begin their work shifts,” says Kaganson. “We also owe it to our highly committed staff to ensure their health and safety as far as possible.”
In order to facilitate quick identification and mitigation, Auria has devised a joint containment and testing strategy that entails all commuting staff being “quarantined” for seven days prior to commencing their 14-day shift.
During this quarantine period, they undergo nasal swab testing by a private pathology lab, and results are received within 24-48 hours. This ensures that once staff commence their 14-day shift, particularly in the high-risk care environment, one can be reasonably certain, both medically and symptomatically, that they are not Covid-19 positive.
“We believe that this maintains a ‘safety bubble’ around our communities, which greatly reduces the chances of transmission by asymptomatic or pre-symptomatic staff,” he says.
“This quarantine affords us the opportunity to get clear test results and prevent any infected persons from entering our communities. It gives us a reasonable period since the last possible exposure to reduce the probability of a ‘false negative’ as well as a reasonable time after the test before a work shift starts to receive the test results.”