Issue 3: Virus stability, risk factors and disinfection (MARCH 19, 2020)
- The National Institute for Allergy and Immune Diseases published in the NEJM on the stability of SARS-CoV-2 vs. SARS-CoV-1 in aerosols and on different surfaces using Bayesian regression modeling1. Viruses were applied as aerosol, and to copper, cardboard, stainless steel, and plastic, and maintained at 21 to 23°C and 40% relative humidity over 7 days.
- Stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested.
- In aerosol: the dose contained 50% TCID. SARS-CoV-2 remained viable in the aerosol for the duration the experiment (3 hrs). TICD/L of air was reduced from103.5 to 102.7 (similar trend for SARS-CoV-1).
- On surfaces: SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours on plastic and 48 hrs on stainless steel after application, but virus titer was greatly reduced from 103.7 to 100.6. Virus titers were <100.5 at 96 hrs.
- No viable virions were found on copper after 4 hrs.
- No viable virions were found on cardboard after 24 hrs.
- The longest viability of both viruses was on stainless steel and plastic; the estimated median half-life of SARS-CoV-2 was approximately 5.6 hours on stainless steel and 6.8 hours on plastic.
- Prolonged viral shedding provides the rationale for a strategy of isolation of infected patients and optimal antiviral interventions2.
- Transmission by aerosol and fomite routes are plausible.
RISK FACTORS FOR COVID-19 PROGRESSION
- A Chinese study reported that age, history of smoking, maximum body temperature on admission, respiratory failure, albumin, and C-reactive protein were significantly associated with progression to pneumonia in COVID-19 patients4.
- Older patients or those with underlying comorbidities are at higher risk of death2,5.
- Refractory patients had older age, male sex, more likely to receive oxygen, mechanical ventilation, expectorant, and adjunctive treatment including corticosteroid, antiviral drugs and immune enhancer (P<0.05).
- The ability of hand hygiene, including hand washing or the use of alcohol-based hand sanitizers to prevent infections is related to reductions in the number of viable pathogens that transiently contaminate the hands.
- Hand washing mechanically removes pathogens, while laboratory data demonstrate that 60% ethanol and 70% isopropanol, the active ingredients in CDC-recommended alcohol-based hand sanitizers, inactivates viruses that are genetically related to, and with similar physical properties as, the SARS-CoV-19 virus.
- The CDC recommends that disposable gloves be worn when cleaning equipment and disinfecting surfaces.
- For disinfection of equipment and surfaces, follow manufacturer’s instructions for application and proper ventilation.
- Unexpired household bleach will be effective against coronaviruses when properly diluted.
- To prepare a bleach solution, the CDC suggests mixing 1/3rd cup of bleach per gallon of water or 4 teaspoons bleach per quart of water .
- Alcohol solutions with at least 70% alcohol, and most common EPA-registered household disinfectants should also be effective6
TCID: Tissue culture infective Dose
*unadjusted global mortality
- Doemalen et al. NEJM March 2020.
- Zhou et al. Lancet, March,11, 2020.
- https://www.cdc.gov/coronavirus/types.html Accessed March 18, 2020
- Liu et al. Chin Med J (Engl) 2020.
- Wang et al. Clin Infect. Dis. March 16, 2020.
- https://www.epa.gov/pesticide-registration/list-n-disinfectants-use-agai… ccessed March 18, 2020.