The Latest Science on COVID-19
On March 9, the European Food Safety Authority announced that there is no evidence that food is a source or transmission route for coronavirus. FDA has taken the same position, both in a stakeholder briefing held on March 18 and in a Food Safety Q&A on its website (updated March 17), in which it noted that foodborne exposure to SARS-CoV-2, which causes respiratory illness, is not known to be a route of transmission, unlike such foodborne intestinal viruses as norovirus and hepatitis A. More details are here.
Persistence on Surfaces
On March 13, The New England Journal of Medicine made available the preprint of a new study (not yet peer-reviewed) by NIH, CDC, Princeton and UCLA scientists on the stability of the novel coronavirus on different types of untreated surfaces. The abstract states: “We found that viable virus could be detected in aerosols [i.e., in the air] up to 3 hours post aerosolization, up to 4 hours on copper, up to 24 hours on cardboard and up to 2-3 days on plastic and stainless steel.”
This was the first such study on the novel coronavirus itself; a meta-analysis of earlier studies on other coronaviruses – SARS, MERS, and the common human coronavirus – was published in February in The Journal of Hospital Infection, and reported persistence of up to 5 days on most hard surfaces and up to 9 days on plastic.
EPA has released a list (last updated March 13) of disinfectants that can be used against the novel coronavirus: but it must be stressed that none of them has actually been fully tested against the virus and approved by EPA for that purpose, although some manufacturers have applied to EPA for expedited review under its Emerging Viral Pathogens Guidance.
The products currently on EPA’s list have, however, shown efficacy on hard non-porous surfaces against the common strains of human coronavirus, SARS and/or MERS, as well as other viruses that are known to be harder to kill, and for the moment it is assumed that they will show similar efficacy against the novel coronavirus. It must be stressed that label instructions as to the length of time that the product should be left on a treated surface (e.g., 30 seconds, 2 minutes, or 10 minutes) for use against a coronavirus should be read and followed carefully.
It has been suggested that the novel coronavirus may be subject to some seasonality, diminishing with the higher heat and humidity of summer but returning in the fall and winter months, rather like influenza, although that is a different type of respiratory virus. The Institute of Virology of the University of Maryland School of Medicine has just reported on its website the results of its examination of the climatic conditions where outbreaks of COVID-19 are currently most prevalent and concludes that the spread of the virus appears to be more restrained in warmer climates, thus giving some support to the seasonality proposal. The full paper, last updated March 17, may be accessed from the website.
On March 16, the journal Science published online a study by an international group of scientists (Li et al.) of the mode of transmission of COVID-19 across China during late January and February. They concluded that, while the transmission rate from undocumented infections was only 55% of the rate from documented infections, the undocumented infections were, due to their greater numbers, the infection source for a massive 79% of documented cases.
They note that undocumented infections often manifest mild, limited, or no symptoms at all, and can, therefore, go unrecognized, with the potential to expose a far greater portion of the population to the coronavirus than would otherwise occur. They suspect that infected individuals may be shedding virus well before the onset of symptoms. Although little can be done about completely asymptomatic individuals other than general travel and similar restrictions, the results of this study indicate it is important that anyone showing even the slightest of symptoms self-quarantine immediately.