[Snorlax94]

Another set of recent preprints that I thought may be of interest
This is NOT SARS-CoV-2, but about the same class of viruses (beta-coronoavirus)
Direct observation of repeated infections with endemic coronaviruses
(This study is also discussed in TWiV 607)
Roughly, 10% of beta-coronavirus infections were followed by repeat infections within a year.

This study provides evidence that re-infections with the same endemic coronavirus are not atypical in a time window shorter than 1 year and that the genetic basis of innate immune response may be a greater determinant of infection severity than immune memory acquired after a previous infection.

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Estimation of SARS-CoV-2 emissions from non-symptomatic cases

Based on models, the study simulated the quantity of virus in the air in a small office or exam room, for asymptomatic cases for breathing alone or for coughing.  Coughing always lead to high numbers (10.9K/cm3 average, 365K/cm3 max) while breathing led to noticeable numbers (0.3/cm3 avg, 11.5/cm3 max).

(Obviously variable for individuals & situations, but roughly 500 cm3 per breath, 15 breaths/min = 7,500 cm3 per minute.)

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Thanks, MT! I appreciate you highlighting these.

The article in repeat infections of coronaviruses goes on to say:

“In contrast, an experimental study on murine coronavirus (MHV), which produces severe, systemic infections in mice, has shown an interplay between virus-specific antibodies and T cells, that upon survival in the host lead to life-long protection against reinfection [18]. Similarly, a longer immunity profile has been hypothesized for SARS and MERS due to their increased severity and to the systemic response that infection induces [14]. Specific antibodies were detectable for at least 2 years in SARS and MERS survivors [19] [20]. Although longitudinal studies on SARS survivors have not detected specific SARS IGG antibody persistence 5 years after infection, they have found that specific memory T cells persist in the peripheral blood of recovered SARS patients, and at higher levels in patients who experienced severe disease [21]. Whether the presence of these memory T cells would be enough to induce a fast, protective response upon reinfection with SARS has not been assessed.”

So hopefully that bodes well for Covid-19.

[Snorlax94]

Another set of recent preprints that I thought may be of interest
This is NOT SARS-CoV-2, but about the same class of viruses (beta-coronoavirus)
Direct observation of repeated infections with endemic coronaviruses
(This study is also discussed in TWiV 607)
Roughly, 10% of beta-coronavirus infections were followed by repeat infections within a year.

This study provides evidence that re-infections with the same endemic coronavirus are not atypical in a time window shorter than 1 year and that the genetic basis of innate immune response may be a greater determinant of infection severity than immune memory acquired after a previous infection.

---

Estimation of SARS-CoV-2 emissions from non-symptomatic cases

Based on models, the study simulated the quantity of virus in the air in a small office or exam room, for asymptomatic cases for breathing alone or for coughing.  Coughing always lead to high numbers (10.9K/cm3 average, 365K/cm3 max) while breathing led to noticeable numbers (0.3/cm3 avg, 11.5/cm3 max).

(Obviously variable for individuals & situations, but roughly 500 cm3 per breath, 15 breaths/min = 7,500 cm3 per minute.)

---

Thanks, MT! I appreciate you highlighting these.

The article in repeat infections of coronaviruses goes on to say:

“In contrast, an experimental study on murine coronavirus (MHV), which produces severe, systemic infections in mice, has shown an interplay between virus-specific antibodies and T cells, that upon survival in the host lead to life-long protection against reinfection [18]. Similarly, a longer immunity profile has been hypothesized for SARS and MERS due to their increased severity and to the systemic response that infection induces [14]. Specific antibodies were detectable for at least 2 years in SARS and MERS survivors [19] [20]. Although longitudinal studies on SARS survivors have not detected specific SARS IGG antibody persistence 5 years after infection, they have found that specific memory T cells persist in the peripheral blood of recovered SARS patients, and at higher levels in patients who experienced severe disease [21]. Whether the presence of these memory T cells would be enough to induce a fast, protective response upon reinfection with SARS has not been assessed.”

So hopefully that bodes well for Covid-19.