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Endemic viruses are often first encountered in childhood. For much of the past year, life in Western Australia has been coronavirus-free. Friends gathered in pubs; people kissed and hugged their relatives; children went to school without temperature checks or wearing masks. The state maintained this enviable position only by placing heavy restrictions on travel and imposing lockdowns — some regions entered a snap lockdown at the beginning of the year after a security guard at a hotel where visitors were quarantined tested positive for the virus.
If other regions, aided by vaccines, aimed for a similar zero-COVID strategy, then could the world hope to rid itself of the virus? In January, Nature asked more than immunologists, infectious-disease researchers and virologists working on the coronavirus whether it could be eradicated.
But failure to eradicate the virus does not mean that death, illness or social isolation will continue on the scales seen so far.
The future will depend heavily on the type of immunity people acquire through infection or vaccination and how the virus evolves. Influenza and the four human coronaviruses that cause common colds are also endemic: but a combination of annual vaccines and acquired immunity means that societies tolerate the seasonal deaths and illnesses they bring without requiring lockdowns, masks and social distancing. In zero-COVID regions there would be a continual risk of disease outbreaks, but they could be quenched quickly by herd immunity if most people had been vaccinated. Five years from now, when childcare centres call parents to tell them that their child has a runny nose and a fever, the COVID pandemic might seem a distant memory.
The virus would become a foe first encountered in early childhood, when it typically causes mild infection or none at all, says Jennie Lavine, an infectious-disease researcher at Emory University in Atlanta, Georgia. Using data from studies, Lavine and her colleagues developed a model that shows how most children first come down with these viruses before the age of 6 and develop immunity to them 1. That defence wanes pretty quickly so it is not sufficient to block reinfection entirely, but it seems to protect adults from getting sick, says Lavine.
Even in children, the first infection is relatively mild. A large study of people who have had COVID suggests that their levels of neutralizing antibodies — which help to block reinfection — start to decline after around six to eight months 2.
But their bodies also make memory B cells, which can manufacture antibodies if a new infection arises, and T cells that can eliminate virus-infected cellssays Daniela Weiskopf, an immunologist at the La Jolla Institute for Immunology in California, who co-authored the study. Weiskopf and her colleagues are still tracking the immune memory of people infected with COVID to see if it persists. If most people develop life-long immunity to the virus, either through natural infection or vaccination, then the virus is unlikely to become endemic, she says.
But immunity might wane after a year or two — and already there are hints that the virus can evolve to escape it. Because the virus has spread around the world, it might seem that it could already be classed as endemic. But because infections continue to increase worldwide, and with so many people still susceptible, scientists still technically class it as in a pandemic phase. In the endemic phase, the of infections becomes relatively constant across years, allowing for occasional flare-ups, says Lavine.Rick Wilson: An Unpunished Coup Is A Training Exercise
To reach this steady state could take a few years or decades, depending on how quickly populations develop immunity, says Lavine. Allowing the virus to spread unchecked would be the fastest way to get to that point — but that would result in many millions of deaths. The most palatable path is through vaccination. Countries that have begun distributing COVID vaccines soon expect to see a reduction in severe illness. But it will take longer to see how effectively vaccines can reduce transmission. Data from clinical trials suggest that vaccines that prevent symptomatic infection might also stop a person from passing on the virus.
If vaccines do block transmission — and if they remain effective against newer variants of the virus — it might be possible to eliminate the virus in regions where enough people are vaccinated so that they can protect those who are not, contributing to herd immunity. Even if the virus remains endemic in many regions, global travel will probably when severe infections are reduced to levels that health services can cope with, and when a high proportion of people who are vulnerable to severe illness have been vaccinated, says Dye.
The influenza pandemic, which killed more than 50 million people, is the yardstick by which all other pandemics are measured. It was sparked by a type of virus known as influenza A, which originated in birds. Almost all cases of influenza A since then, and all subsequent flu pandemics, have been caused by descendants of the virus.
These descendants circulate the globe, infecting millions of people each year. Flu pandemics occur when populations are naive to a virus; by the time a pandemic virus becomes seasonal, much of the population has some immunity to it. Seasonal flu still has a ificant toll globally, claiming roughlylives per year.WHAT IF 1000 COCKROACHES RELEASED IN LARGE ANTHILL IN A TRANSPARENT CUBE? VERSUS ANTS
US commuters and telephone operators wore face masks in the influenza pandemic. Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle, thinks the coronavirus might follow a similar path. Shaman and others say the virus could also settle into a seasonal pattern of annual winter outbreaks similar to flu. Still, the coronavirus might be able to dodge immunity acquired by infection, and possibly outsmart vaccines. Already, laboratory studies show that neutralizing antibodies in the blood of people who have had COVID are less capable of recognizing a viral variant first identified in South Africa called Y.
V2than variants that circulated earlier in the pandemic 4. Trial suggest that some vaccines might be less effective against Y. V2 than against other variants, and some vaccine makers are exploring redes of their products. Still, the immune system has lots of tricks up its sleeve, and can respond to many features of the virus, not just spike, says Lavine.
Preliminary trial also suggest that vaccines can protect people with Y. V2 against severe disease, says Rasmussen. This would not be a first for a human coronavirus. In a study 5 yet to be peer reviewed, Bloom and his colleagues show that the endemic coronavirus E has evolved so that neutralizing antibodies in the blood of people infected with the viral variant circulating in the late s and early s are much less effective against more recent variants.
People are reinfected with E over their lifetime, and Bloom suspects that it might be harder to stave off the variants that have evolved to escape immunity. But even then, immunity from either past vaccination or infection will probably blunt serious disease, he says. And Lavine notes that even if people are reinfected, this might not be a big deal. With the endemic coronaviruses, frequent reinfections seem to boost immunity against related variants and typically people experience only mild symptoms, she says.
With a highly effective measles vaccine — two doses and a person is protected for life — the measles virus has been eliminated in many parts of the world. Before a vaccine was developed inmajor epidemics killed about 2. Unlike flu vaccines, the immunization for measles has never needed to be updated because the virus has yet to evolve in ways that evade the immune system. Measles is still endemic in parts of the world with insufficient immunization.
Ina global resurgence killed more thanpeople. A survey of more than 1, US citizens found that more than one-quarter would definitely or probably decline a COVID vaccine, even if it were free and deemed safe see go. Several diseases brought under control persist because animal reservoirs, such as insects, provide chances for pathogens to spill back into people.
These include yellow fever, Ebola and chikungunya virus. SARS-CoV-2 probably originated in bats, but it might have passed to people through an intermediate host. The virus can readily infect many animals, including cats, rabbits and hamsters. It is particularly infectious in mink, and mass outbreaks on mink farms in Denmark and the Netherlands have led to huge animal culls. The virus has also passed between minks and people. If it became established in a wild-animal population and could spill back into people, it would be very difficult to control, says Osterholm.
The path that SARS-CoV-2 might take to become an endemic virus is challenging to predict, but society does have some control over it.
In the next year or two, countries can reduce transmission with control measures until enough people have been vaccinated either to achieve herd immunity or to drastically reduce the severity of infections. That would ificantly reduce deaths and severe disease, says Osterholm. Lavine, J. S, Bjornstad, O. Article Google Scholar. Dan, J. Scienceeabf PubMed Article Google Scholar. Hogan, A. Cele, S. Eguia, R. Download references. News 15 OCT Article 14 OCT News 14 OCT Yale University.
Francis Crick Institute. Aarhus University AU. Advanced search. You have full access to this article via your institution. Download PDF. Source: Nature survey. References 1. Article Google Scholar 2. PubMed Article Google Scholar 3. Close banner Close.
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