Chronicle Editor
Noel Munzabwa
Zimbabwe has just gone from a 100 percent imported Covid-19 cases to a good number of locally-acquired cases, raising a stubborn but sad probability of undocumented asymptomatic but highly infectious people in our communities.
Confirmed cases with no history of travel to the pandemic hotspots nor known contact with any of the registered cases popped up last week not just in Zimbabwe but even Eswatini.
Just how possible is this? This is the big question we ought to answer if we are to understand the #LOCKDOWN called which was further extended by most countries in the last couple of days which also coincided with peaked daily new infections.
Between Friday and Saturday, South Africa recorded the highest ever lockdown period daily peak with 251, Eswatini added three to get to 22, Botswana added five – merely two days after Zimbabwe jumped from 18 to 23 adding five in a single day.
Is it possible to be infected with the coronavirus and show no symptoms? Or go through a period of several days before symptoms kick in? Just how many people are mingling in the population without knowing they’ve been infected with the coronavirus?
Truly it is getting risky not to adhere and perhaps we need to borrow from the electricians’ world that treats all naked wires as live and wear caution that potentially Covid-19 is everywhere – hence the need to protect ourselves and protect the next person.
Most worrying was the fact that the statistic scales continued to tilt more to the locally acquired infections outpacing the imported cases percentage but credit has to go to authorities especially in Zimbabwe where vigilant contact tracing is yielding results.
Indeed true to the stats the world equally acknowledges there is significant transmission by people not showing symptoms if recent statistics unravelling newly confirmed Covid-19 cases with no history of travel to hotspots nor known contact with recorded cases is anything to go by.
Stephen Morse, an epidemiologist at Columbia University, told Business Times recently his most worrying source of possible new infections that should surely send arrogant free roamers into strict lockdown.
“We don’t know all the unidentified cases out there, it’s mostly sicker people in hospitals who are being tabulated,” Morse said.
The prevalence of asymptomatic transmission doesn’t bode well for global containment efforts, as Bill Gates recently wrote in the New England Journal of Medicine.
“That means Covid-19 will be much harder to contain than the Middle East respiratory syndrome or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people,” Gates said.
In the context of Covid-19, just what is the difference between an imported case from locally acquired case, more so what is contact tracing?
The term imported case refers to cases with a history of having travelled to hotspots or potential hotspots while locally acquired cases refers to those who may have contracted the virus from contact with recorded cases locally and have no history of having travelled to hotspots. Locally acquired also refers to cases that have no history of travel to hosts nor have no known contact with recorded cases.
It is the latter that is freaking scary to our citizens as the source of contact is from unrecorded and unknowing asymptomatic (has no signs and symptoms associated with Covid-19) but highly infectious individuals. Just imagine the potential risk.
That’s because the Covid-19 virus is insidious.
According to Anthony Fauci, director of the US’ National Institute of Allergy and Infectious Disease, “somewhere between a quarter and half” of people infected with the new coronavirus may never show symptoms or fall ill — but can still transmit the illness to others.
Robert Redfield, director of the US’ Centres for Disease Control and Prevention, gave NPR a similar estimate on March 31, suggesting that asymptomatic carriers are contributing to the rapid spread of the coronavirus
During a White House briefing on April 5, Fauci cautioned that these percentages are just estimates, and said there is disagreement even among his colleagues as to how many people are asymptomatic. He added that antibody tests — which can confirm whether a person has already had Covid-19 — are needed to answer that question “in a scientifically sound way.”
Yes it is possible to be infected with the coronavirus and show no symptoms or go through a period of several days before symptoms kick in with no cough, no fever, no sign of illness, and could be transmitting the virus to others.
“There is evidence that SARS-CoV-2 has this ability to spread silently,” says Shweta Bansal, an infectious disease modeler at Georgetown University.
Indeed, cases of Covid-19 among nursing home residents, choir groups and families fuel a growing concern about people who are infected, yet feel generally OK and go about their daily lives, giving the virus to friends, family members and strangers without knowing that they themselves have it.
But there are wide gaps in our understanding of how many people fit this category of “silent spreaders” — as they’re called by some public health researchers — and how much they contribute to transmission of the disease.
Silent spreaders can be divided into three categories: asymptomatic, presymptomatic and very mildly symptomatic.
Asymptomatic: people who carry the active virus in their body but never develop any symptoms.
It’s hard to figure out when someone has a disease but shows no signs of it.
Some cases of asymptomatic carriers have been confirmed by finding and testing people who were in close contact with Covid-19 patients. For those who tested positive without symptoms, follow-up exams confirmed that about a quarter continued to show no signs, World Health Organisation officials said on April 1, citing data from China.
No one can truly determine the impact of asymptomatic cases on spread until there’s more testing. But so far, they have made up a sliver of the total number of people who’ve tested positive. And the affected individuals seem to skew young.
Presymptomatic: people who have been infected and are incubating the virus but don’t yet show symptoms.
After infection, symptoms might not develop for five to six days — or even two weeks, according to the Annals of Internal Medicine. The time between catching the virus and showing symptoms is called the presymptomatic phase.
People appear to be most infectious right around the time when symptoms start, said Maria Van Kerkhove, technical lead for the WHO’s Health Emergencies Programme, at an April 1 news conference.
So far, presymptomatic is a much more common category than asymptomatic. About three quarters of people who test positive without showing symptoms turn out to be presymptomatic, displaying coughing, fatigue, fever and other signs of Covid-19 in a later follow-up exam, said Van Kerkhove.
This suggests that “transmission from asymptomatic and presymptomatic residents, who were not recognised as having SARS-CoV-2 infection and therefore not isolated, might have contributed to further spread,” according to research published in the CDC’s April 3 “Morbidity and Mortality Weekly Report.”
A study in Singapore found similar evidence of presymptomatic spread among people who went to church, took singing classes or puttered at home with their spouses.
Very mildly symptomatic: people who feel a little unwell from a Covid-19 infection but continue to come in close contact with others.
“We’re very lucky that this isn’t a severe infection for everyone, but because of that, some people feel a little sick and power through,” says Seema Lakdawala, a flu researcher at the University of Pittsburgh.
Spreading Covid-19 while having a cough or very mild fever doesn’t fully count as silent transmission, says Bansal, the infectious disease modeler: “There’s some signal there at least.”
But people who continue to frequent communal and public places with a light cough or mild fever may unwittingly spread the disease in the early days of symptom onset — the time they’re thought to be most infectious.
Dr Robert Redfield, director of the Centres for Disease Control and Prevention, told NPR in an interview on April 9 that while he thinks “asymptomatic spread was and is more significant than was appreciated back in January, the relative contribution of asymptomatic spread to symptomatic spread has not been clearly defined.”
Even though there is still much to learn about silent spreading, the concerns about this mode of transmission give more weight to the advice we’ve been hearing all along: Keep a two-metre distance from others, wash hands often and wipe down surfaces.
In conclusion, maximum vigilance is required as there is a strong possibility of undocumented asymptomatic but highly infectious people in our communities. One needs to take full responsibility to first protect himself or herself from contracting the virus without a government push. That way we will be able to protect the next person, the country and the world. — @NoelMunzabwa.
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