Like measles, covid-19 could become endemic. Never dying out entirely. Needing to be controlled in human denser populations into the indefinite future.
This is the warning from the WHO.
Speaking at a briefing on Wednesday, WHO emergencies director Dr Mike Ryan warned against trying to predict when the virus would disappear.
“It is important to put this on the table: this virus may become just another endemic virus in our communities, and this virus may never go away,” Dr Ryan told the virtual press conference from Geneva.
“HIV has not gone away – but we have come to terms with the virus.”
Dr Ryan then said he doesn’t believe “anyone can predict when this disease will disappear”.
There are currently more than 100 potential vaccines in development – but Dr Ryan noted there are other illnesses, such as measles, that still haven’t been eliminated despite there being vaccines for them.
WHO Director-General Tedros Adhanom Ghebreyesus stressed it was still possible to control the virus, with effort.
“The trajectory is in our hands, and it’s everybody’s business, and we should all contribute to stop this pandemic,” he said.
WHO epidemiologist Maria van Kerkhove also told the briefing: “We need to get into the mindset that it is going to take some time to come out of this pandemic.”
While I’m not a doctor, over the years I have looked at the history of diseases in human populations in my reading and courses. That is where I think that this disease will wind up. If I had to bet, and assuming a vaccine, I’d say this will eventually be more prevalent than measles, and less frequent outbreaks than the annual flu. It will be endemic.
In epidemiology, an infection is said to be endemic (from Greek ἐν en “in, within” and δῆμος demos “people”) in a population when that infection is constantly maintained at a baseline level in a geographic area without external inputs. For example, chickenpox is endemic (steady state) in the UK, but malaria is not. Every year, there are a few cases of malaria reported in the UK, but these do not lead to sustained transmission in the population due to the lack of a suitable vector (mosquitoes of the genus Anopheles).Wikipedia – endemic
The difference from measles is that it seems likely that any conferred immunity getting covid-19 or from a vaccine will be temporary. Unlike measles which generally gives a life-long immunity, the corona viruses in human populations often appear to only give a few years immunity.
We simply haven’t observed this disease for long enough to be able to say that with any definition. But there is a lot of attention being paid to looking at reinfection rates, because this has obvious implications in public policy.
There is a particularly good article in the US NPR (National Public Radio) looking at different aspects of immunity with the corona virus family and with covid-19 in particular.
Antibodies, which are proteins found in the blood as part of the body’s immune response to infection, are a sign that people could be developing immunity. But antibodies are by no means a guarantee a person will be protected for life — or even for a year.
Shaman has been studying four coronaviruses that cause the common cold. “They’re very common and so people seem to get them quite often,” Shaman says. Ninety percent of people develop antibodies to those viruses, at least in passing, but “our evidence is those antibodies are not conferring protection.
That may be simply because colds are relatively mild, so the immune system doesn’t mount a full-blown response, suggests Stanley Perlman, a pediatrician who studies immunology and microbiology at the University of Iowa. “That’s why people get colds over and over again,” he says. “It doesn’t really tickle the immune response that much.”
He’s studied one of the most severe coronaviruses, the one that causes SARS, and he’s found that the degree of immunity depended on the severity of the disease. Sicker people remained immune for much longer, in some cases many years.
For most people exposed to the novel coronavirus, “I think in the short term you’re going to get some protection,” Perlman says. “It’s really the time of the protection that matters.”
Perlman notes that for some people the symptoms of COVID-19 are no worse than a cold, while for others they are severe. “That’s why it’s tricky,” he says, to predict the breadth of an immune response.
And it’s risky to assume that experiences with other coronaviruses are directly applicable to the new one.
Nadeau is working on several studies, including one that seeks to recruit 1,000 people who were previously exposed to the coronavirus. One goal is to identify people who produce especially strong, protective antibody responses. She says the antibody-producing cells from those people can potentially be turned into vaccines.
Another critical question she’s zeroing in on is whether people who become immune are still capable of spreading the virus.
“Because you might be immune, you might have protected yourself against the virus,” she says, “but it still might be in your body and you’re giving it to others.”
It would have huge public health implications if it turns out people can still spread the disease after they’ve recovered. Studies from China and South Korea seemed to suggest this was possible, though further studies have cast doubt on that as a significant feature of the disease.
More questions than answers so far. But as the people from the WHO have been pointing out, unlike SARS, it looks like covid-19 is unlikely to die out in the world population.
So New Zealand should probably start planning on it being present in those 4 million tourists who used to flood our shores every few years. Because after all the growth pattern for covid-19 looks like the grim reality of this graphic. It only takes a few people spreading and a reduced level of immunity in a population, and social distancing becomes the only viable public health measure.