The ongoing pandemic of a respiratory infectious disease known as COVID-19 which started in December 2019 has occasioned an explosion of information and an outburst of myths. This has been described as an infodemic. More interesting to me as an epidemiologist and teacher are the medical and epidemiologic terms that it has introduced into common parlance. This outburst of unfamiliar words into public discourse has brought with it a terminological laxity, imprecision, and confusion, common even among public health specialists and epidemiologists.
Self-isolation or self-quarantine?
The Director-General of the Nigeria Centre for Disease Control (NCDC) spent 10 days in China as a member of a WHO team of experts. Back in the country, he immediately restricted himself to his house as prescribed by the surveillance protocol for a period of two weeks.
During this period, the minister of health went on air to say that the disease control agency boss was quarantined at home after return from China. This pronouncement rent the airwaves. Journalists were confused. As if to correct the minister, the NCDC DG was reported to have said that he was not quarantined but was in self-isolation. Who was right – the minister or the DG? Or where they saying the same thing using diffetent words? This caused a lively debate and a not a little brouhaha in my med school graduating class WhatsApp group. Which is which: was he in quarantine, isolation, self-quarantine or self-isolation?
In many Emergency Operations Centre meetings that I have attended, I noticed that people have used the terms self-quarantine and self-isolation interchangeably. I have encountered the same in many newspapers and magazines, including The Economist. And on the television, local and international. But are the two terms really synonymous? The A Dictionary of Epidemiology, the most authoritative lexicon in the field, makes clear that the essential distinction is clinical: while quarantine applies to healthy people who have been exposed to a disease and could be incubating it, isolation refers to separating and restricting the movement of people who have been diagnosed with a disease to prevent its spread. So, properly speaking, the DG was in self-quarantine and not self-isolation.
Most people often use quarantine and isolation correctly unless when it is voluntary. I think many people tend to say self-isolation when they mean self-quarantine for a number of reasons. It is probably as a result of a hold-over from the days when quarantine meant something that happened at the ports when ships carrying people suspected of incubating a disease had to wait for forty days (quaranta giorni in Italian) before being allowed to disembark. It was not something that happened in the community like self-quarantine. The other thing is that quarantine has a legal dimension. It is a ‘police power’ function, it can be enforced. But this aspect has been taken care of by the qualifying word ‘self’, showing that it is voluntary. Hence, it is also known as voluntary quarantine. And many people just use the inaccurate expression the way we learn and use language – unconscious imitation. Further, it doesn’t help that what is more properly referred to as cordon sanitaire — the restriction of people in and out of a defined geographical area — is also more commonly called quarantine.
As an amateur word-watcher, I know that prevailing usage often determines accepted — and therefore correct — usage. Words and expressions bear the meanings that the majority of people give them. But I think it is useful to maintain the distinction between the two terms.
Some technically inaccurate usages have a way of persisting that they become almost acceptable, even among specialists. One of such in epidemiology is the expression, ‘prevalence rate’. It is a misnomer because prevalence is a straightforward proportion and certainly not a rate, as it has no time component. This one I have little patience for — I still correct it while reviewing reports from trainees or manuscripts for peer-reviewed journals.
The virus and the disease
At the beginning of the outbreak, the novel virus was called 2019-nCoV but the respiratory disease it causes did not have a proper name. A few weeks later the disease was christened COVID-19 (i.e. coronavirus disease first described in 2019). The virus itself was renamed SARS-CoV2. Many people didn’t appreciate exactly what happened. For them, COVID-19 merely replaced 2019-nCoV. On March 6, the genetic sequencing result of the virus from the imported case in Nigeria was published online, with the title “First African SARS-CoV2 genome sequence from Nigerian COVID-19 case”. A friend, an experienced epidemiologist, commented, “Does this mean the guy does not have COVID-19 but SARS COV2?”. It is clear from the statement that he didn’t get the relationship between the two terms — I had to explain that SARS-CoV2 is the virus while COVID-19 is the disease, using the analogy of HIV (the virus) and AIDS (the disease).
Is it local transmission or community transmission?
At the onset of the outbreak, for the purposes of surveillance at the airports, we only considered travelers from China as high-risk travelers who should be monitored for a period of two weeks. In a few weeks, Iran, South Korea and Italy had joined the list. We kept saying that those four countries were the ones with community transmission. However, up to March 11, the WHO daily situation report continued to classify Iran, South Korea, and Italy as having local transmission, rather than community transmission. So, what is the difference? The definitions offered by WHO are hardly helpful. On its website, it says that while community transmission is evidenced by the inability to relate confirmed cases through chains of transmission for a large number of cases, or by increasing positive tests through sentinel samples (routine systematic testing of respiratory samples from established laboratories), local transmission indicates locations where the source of infection is within the reporting location. In simple terms, if the source of the cases can be traced, it is local transmission. But when cases are cropping up which can’t be linked to a source, it is community transmission. For instance, what we currently have in Nigeria as at March 12 is local transmission. The second case is a contact of the imported case that was tested and found positive. Both of the cases were reported from Ogun State. But imagine that someone presents to a hospital in Kaduna State and tests positive without a history of travel to a high risk country and without a history of contact with the Ogun State cases, that would be community transmission. From these definitions and what actually obtains in many countries, it is clear that the WHO inaccurately continues to classify a number of countries with community transmission as having local transmission. The term ‘local transmission’ is infrequently used in both medical literature and news reportage.
When did it become a pandemic?
After warding off the question of whether the COVID-19 for several days, the WHO on March 11 officially declared the outbreak a pandemic. But did it just become a pandemic that Wednesday afternoon? In fact, the outbreak had been referred to as a pandemic for weeks by epidemiologists. In public health school, we learnt that a pandemic is simply a global outbreak — an outbreak that has affected all the continents in the world. And that’s why the expression ‘global pandemic’ is tautological. What criteria did the WHO use in this outbreak? Did it use the criteria of community-wide outbreaks in multiple countries in multiple WHO regions used during the 2009 H1N1 pandemic? In the Director-General’s briefing, he hinted at this when he said ‘spreading in multiple countries around the world at the same time’. But that had been going on for days, if not weeks, before the declaration was made. I think the global health agency was careful not to tip countries into a panic and give up on preparedness. The word has political and diplomatic consequences beyond its lexical and technical, meaning. It has policy and response implications. It is clear that the guys in Geneva had learnt a lesson from the severe criticism they faced in the aftermath of the H1N1 pandemic of 2009. Many claimed that WHO unduly exaggerated the threat and caused great panic Many even charged it with conflict of interest. They claimed that WHO declared a ‘false pandemic’ to help pharmaceutical companies to sell vaccines. And this was despite the fact that the declaration of phase 6 (full-fledged pandemic) was delayed until the sustained community spread in multiple countries in multiple WHO regions was indisputable. This time around, the WHO was just being cautious.