Scientists have raised the possibility that COVID-19 will not be wiped out but will come back every winter, as influenza usually does.

Some recent respiratory diseases caused by novel viruses, such as SARS in 2002 and MERS in 2012, have been contained before they become seasonal. With fewer people infected it has been possible to identify and isolate people with the virus quickly, so preventing spread from person to person.

One problem with COVID-19 is that many people carrying the virus have had mild or few symptoms, and it is thought that without safe distancing one person with the virus can infect about three others who are not immune. That means the virus can pass to many people without them realising it.

We do not yet know what will happen later in this pandemic. Numbers of cases are reducing now because of strict social distancing measures. Scientists can’t predict what will happen after those measures are eased, but it is possible the virus will be around for years to come.

Where did the story come from?

Several media outlets reported a briefing given by Chinese scientists on 27 April, where Jin Qi, director of the Institute of Pathogen Biology at the Chinese Academy of Medical Sciences, said: “This is very likely to be an epidemic that co-exists with humans for a long time, becomes seasonal and is sustained within human bodies.”

What is the basis for the claim?

The Chinese scientists said their testing campaigns had discovered many people carrying the SARS-CoV-2 virus which causes COVID-19, who did not have symptoms.

Researchers from Harvard Medical School have modelled several possible ways in which the virus could spread over the next 5 years. They used data about two coronaviruses which cause the common cold as a model, plus the information we have so far about SARS-CoV-2.

They found that much depends on how long people who have had the virus remain immune to it. Immunity could last for as little as 40 weeks (as in the common cold coronaviruses) or could be longer-lasting. If immunity is only 40 weeks, then yearly outbreaks are more likely.

The size of outbreaks will also depend on what time of the year the outbreak starts, with outbreaks in autumn likely to lead to higher peaks in infection. The pattern will depend on the degree to which the disease is affected by colder and warmer weather. The researchers predict that, if effective treatments or a vaccine can’t be found, then intermittent social distancing measures could be needed until 2022 to avoid overwhelming demand on health services. They predict that “recurrent wintertime outbreaks of SARS-COV2 will probably occur” after the first pandemic wave.

It’s important to be aware that all these studies have underlying uncertainties. Until we know some of the missing information – such as how long any immunity lasts – we can’t really predict accurately what will happen in the future.

What do trusted sources say?

There is currently no advice for the public about how to prepare for winter outbreaks in the northern hemisphere. Though it is possible that other countries will have data to inform us soon.

The Center for Disease Control in the US has said that it is not yet known whether the weather and temperature will affect the spread of COVID-19. They add “there is much more to learn about the transmissibility, severity, and other features associated with COVID-19 and investigations are ongoing”.

Analysis by EIU Healthcare, supported by Reckitt Benckiser

 

Citation

  1. Kissler S et al. Projecting the transmission dynamics of SARS-Cov-2 through the postpandemic period. Science 2020 10.1126/science.abb5793

Reading list

  1. Virus Likely to Keep Coming Back Each Year, Say Top Chinese Scientists. Bloomberg https://www.bloomberg.com/news/articles/2020-04-28/virus-is-here-to-stay-and-likely-seasonal-say-china-scientists (Accessed 13 May 2020)