Coronavirus (COVID-19): As coronavirus cases continue to surge across the world and millions are confined to their homes, governments are still thinking about how and when lockdowns can be lifted so that normalcy can resume. With a vaccine at least 12-18 months away, scientists and researchers are now looking into what the post pandemic transmission of SARS-CoV-2 can look like and the possible measures that might be needed to control future outbreaks.
A new study published in Science looks at what will happen after the initial, most severe pandemic wave passes.
The post pandemic possibilities: What the research states
Researchers have noted two possibilities. The SARS-CoV-2 virus could be eradicated through public health measures, just as its closest genetic relative SARS-CoV-1 was. Public health authorities, however, do not consider this a likely outcome.
Alternatively, the transmission of the virus could be similar to the influenza pandemic, which circulated seasonally after the initial global wave of infections. Researchers have reason to believe there could be recurrent wintertime outbreaks of COVID-19.
What factors will influence post pandemic transmission of SARS-CoV-2?
The post pandemic transmission of SARS-CoV-2 could depend on various factors. First, it will depend on the whether the transmission of coronavirus changes with seasons. (Read our explainer on whether the summer’s heat will kill coronavirus)
Second, it remains uncertain as to whether immunity from the virus is permanent. Which is to say, for how long a person can remain immune to SARS-CoV-2 without contracting the disease again. If the immunity is short term (40 weeks), such as in the case of HCoV-OC43 and HCoV-HKU1, researchers project that the virus will cause annual outbreaks. On the other hand, if the immunity is for a longer period (about two years), the virus may lead to biennial outbreaks.
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Third, researchers are studying the degree of cross-immunity between SARS-CoV-2 and other coronaviruses. Cross-immunity means if getting infected by one type of coronavirus can protect against the other. For instance, a person infected with SARS-CoV-1 can generate neutralising antibodies against HCoV-OC43 (a common cause of common cold). Similarly, getting infected with HCoV-OC43 can enable the generation of antibodies against SARS-CoV-1.
When compared with other coronaviruses, SARS-CoV-2 may appear to be milder than SARS-CoV-1 and MERS, but more severe than HCoV-OC43 and HCoV-HKU1. What makes SARS-CoV-2 difficult to control is its high infectiousness at the start of onset of mild symptoms.
Last, the intensity and timing of mitigation measures will determine the future spread of the disease.
Taking into account these factors, researchers have projected that in all modelled scenarios, SARS-CoV-2 is capable of producing substantial outbreaks. They project that a winter/spring outbreak will produce lower peaks, while an autumn/winter outbreak will produce more acute peaks.
So what does this mean?
If the immunity from SARS-CoV-2 is long-term then the virus could effectively disappear for five or more years after causing a major outbreak. If immunity from the virus is relatively short-term, which is for a period of two years and considering that there is some degree of cross-immunity against SARS-CoV-2 from HCoV-OC43 and HCoV-HKU1, then the transmission of the virus could be eliminated for a period of three years, after which, it may resurge in 2024.
Researchers maintain that regardless of the post pandemic transmission dynamics of the virus, “urgent measures” are required to address the ongoing crisis, which includes non-pharmaceutical interventions (NPIs) given that vaccine development may take months to years. For instance, social distancing is one such NPI being used by various countries where there is a widespread transmission of this disease.
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As per the researchers modelling, there will be a resurgence of infection once social distancing restrictions are lifted. “However, longer and more stringent temporary social distancing did not always correlate with greater reductions in epidemic peak size,” they noted.
Even so, immunity from the disease is one of the crucial factors that will determine if the virus will potentially die out or resurface in annual or biennial outbreaks.
Further, a one-time social distancing measure may push the epidemic peak, while intermittent social distancing measures will continue to keep critical care measures within their current thresholds. The researchers said “widespread surveillance will be required to time the distancing measures correctly and avoid overshooting critical care capacity.”
Also, intermittent social distancing measures need to be used in tandem with contact tracing and quarantine efforts.
“To shorten the SARS-CoV-2 epidemic and ensure adequate care for the critically ill, increasing critical care capacity and developing additional interventions are urgent priorities,” the researchers concluded.
Serological testing is required to determine and understand the extent and duration of immunity to SARS-CoV-2, which in turn will influence what the post-pandemic scenario looks like.
Apart from this, “widespread surveillance” is required in the short term to implement intermittent social distancing effectively and to prepare for the possibility that there may be resurgences of the virus as late as 2025, “even after a prolonged period of apparent elimination”.
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