(1) So what other coronaviruses are there in humans? So far, seven such viruses have been found to be pathogenic in humans. Three of these can be fatal: SARS-CoV-1 (the original 2002-3 SARS virus), MERS (Middle East Respiratory Syndrome virus), and of course SARS-CoV-2, the causal agent of COVID19.
So what about the other four? These turn out to cause about 15% of all common colds. Over 200 different viral types (half of them rhinoviruses) are associated with common colds. Rhinoviruses account for the majority of all common cold cases; influenza viruses a for another 10-15%; adenoviruses (a group of non-enveloped DNA viruses) account for another 5% or so, besides causing conjunctivitis and some forms of viral gastroenteritis (“stomach flu”).
In temperate climates, common-cold coronaviruses (CCCoV) are seasonal; in tropical climates they act year-round. They are:
- HCoV-NL63, first identified in The Netherlands. which accounts for almost 5% of common respiratory illnesses. “Associated diseases include mild to moderate upper respiratory tract infections, severe lower respiratory tract infection, croup and bronchiolitis.” The severe cases are rare and usually involve young children, the elderly, and immunocompromised patients
- HCoV-HKU1, first identified in Hong Kong. This one is presently quite rare
- HCoV-OC43, believed to be a milder mutant of the pathogen that caused the 1889-1890 flu pandemic. Don’t miss Matt Ridley’s article on that one (linked here previously).
- HCoV-229E, which is fairly common: apparently as many as half of young children have had a previous infection with this one. While it’s associated with some severe clinical outcomes, there is almost always another pathogen involved too: a single case of ARDS (acute respiratory distress syndrome) without involvement of another pathogen has been documented.
Now unlike the rhinoviruses, where there is almost no cross-immunity between their 99 different strains (hence, you can get several common colds over the course of a single winter), there appears to be very significant cross-reactivity between the different coronaviruses, with as many as 40-50% of the population being partly or fully immune toward SARS-CoV-2 due to previous exposure to one of the four CCCoVs. It seems that the immune system latches onto the “spikes” that all coronaviruses have in common (and effect their entry into cells), so if your T-cells “have seen one, they’ve seen them all”…
As Matt Ridley has argued, OC43 may be a hint of what will be the endgame for SARS-CoV-2: evolutionary pressure for viruses is toward a more virulent (shorter incubation time, faster entry) but less deadly form, as killing off the host doesn’t help the spread. So it may well become “the fifth CCCoV”.
(2) Two Israeli companies market antibacterial and antiviral face masks claiming to protect against COVID19: SonoviaTech and Argaman (the Hebrew word for the color crimson). Full disclosure: I have no commercial or scientific links to either company, although I know some of the people involved by reputation.
Note that neither mask was developed for this purpose: both companies are in the business of developing solutions for the prevention of hospital-acquired bacterial infection. (As so many “hospital bugs” are increasingly resistant to every antibiotic we can throw at them, bactericidal solutions to prevent infection are becoming increasingly topical, especially in operating rooms and ICUs but not just there.) The initial impetus for Argaman was actually when the founder (a cancer survivor) was in chemotherapy — he remembered thinking everybody coming in would be immunocompromised, and wouldn’t the Cupron copper-infused antibacterial fabric he helped develop come in handy for antibacterial face masks…
From what I understand, Argaman’s tech is based on a combination of Cupron and an N95-type filter. Sonovia instead appears to be based on lacing a cotton-like fabric with nanocavities through sonication [Bar-Ilan U. Professor emeritus Aharon Gedanken, a pioneer in this area, is a consultant to the company], then depositing nanoparticles of zinc oxide and copper into the cavities.
Both mask types are intended for extended reuse (as long as 1 years, with gentle washing once a week). Thus, despite their fairly steep prices ($50 apiece for Argaman regardless of quantity; Sonovia is more expensive for single masks but cheaper in bulk) they will save money in the long term over N95.
Veteran ER nurse “Sandy” has posted video reviews of the Sonovia and Argaman masks. (Here she suggests a useful improvement to the Sonovia — an adhesive nose clip which they will apparently add to future versions.)
I got curious about them and ordered a 3-pack of female-sized Sonovia masks, which arrived yesterday, and will order the Argaman as well. I will post a review of both after I receive the Argaman.