Genetic sequencing of COVID-19 in China in December 2019 revealed two strains of the virus, identified as S and L, with S being the ancestral version while L was more prevalent (70:30 ratio) and more virulent.

In December, I and all my family (in the UK) experienced a viral illness of severity somewhere between a cold and influenza, which we all independently declared was strikingly different in character to any cold or flu we had previously experienced. We experienced mild headaches, mild bodily aches and a dry cough. Notably it really dragged on, for three weeks or possibly more. My fit and healthy mum (aged around 70) suffered fairly severe respiratory distress (not so severe she required hospitalisation) and we were quite worried about her.

Fast forward to now, and this experience obviously takes on a new perspective. What can we say about the probability this illness was some coronavirus (not necessarily COVID-19)? What's the likelihood it was one of the two strains of COVID-19? Do we know, or can we estimate the likelihood, that any antibodies to any given coronavirus confer some immunity to other strains?

What I do know of this, is that there are known cases of people becoming ill again with COVID-19, having earlier been declared virus free - it's unknown whether they caught one strain then the other, or became reinfected with the same one twice, or the virus increased in activity again.

  • What is the source for your claim that there are known cases of people being reinfected with COVID-19?
    – Carey Gregory
    Commented Mar 12, 2020 at 14:51
  • @CareyGregory actually good point, what we know is that some people relapse. It's unknown whether they have become reinfected or whether the original infection has become active again. upi.com/Health_News/2020/03/06/… Commented Mar 12, 2020 at 18:22
  • 4
    Thanks. When you add info to a question, it's always best to edit the question and add it. (I did that for you.)
    – Carey Gregory
    Commented Mar 12, 2020 at 19:47

1 Answer 1


I doubt we have data to answer this question but since flu like illnesses keep recurring year after year as the virus mutates then it seems unlikely that exposure to something which most people get has had any benefit to those being exposed to the novel coronavirus SARS-CoV-2.

In general, estimates suggest that 2% of the population are healthy carriers of a CoV and that these viruses are responsible for about 5% to 10% of acute respiratory infections.[3]

Common human CoVs: HCoV-OC43, and HCoV-HKU1 (betaCoVs of the A lineage); HCoV-229E, and HCoV-NL63 (alphaCoVs). They can cause common colds and self-limiting upper respiratory infections in immunocompetent individuals. In immunocompromised subjects and the elderly, lower respiratory tract infections can occur.

Other human CoVs: SARS-CoV, SARS-CoV-2, and MERS-CoV (betaCoVs of the B and C lineage, respectively). These cause epidemics with variable clinical severity featuring respiratory and extra-respiratory manifestations. Concerning SARS-CoV, MERS-CoV, the mortality rates are up to 10% and 35%, respectively.

Furthermore, the fact that there have been no or near no deaths amongst children raises the speculative possibility that previous exposure might make the illness worse since children have fewer years of exposure to seasonal coronaviruses.


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