Summary of Coronavirus disease 2019 (COVID-19) Examine.com March 5, 2020
First, understand these four key terms:
1. SARS-CoV-2
The current virus is NOT called "COVID-19"! COVID-19 is the infectious disease caused by the virus. SARS-CoV-2 is the name of the actual virus, due its genetic similarity to the original SARS virus. It’s short for “Severe Acute Respiratory Syndrome Coronavirus 2”.[4] For more information on the virus structure and properties, see the "Sources and Structure" part of our research breakdown.
2. COVID-19
There are seven coronaviruses that can cause human disease, with the three most severe diseases being SARS, MERS, and COVID-19.[5] The 2020 COVID-19 epidemic is notable because it's a new virus in humans, spreading much faster and wider globally than did SARS or MERS, with a high mortality rate compared to the seasonal flu.[6] The other four coronaviruses (called HCoV 229E, NL63, OC43, and HKU1) have long been widespread globally, and cause 10%-30% of upper respiratory tract infections in adults.[7]
COVID-19 has around twenty times the mortality rate of the seasonal flu, at around 2% of people infected, versus the flu at around 0.1%.[8][9] The COVID-19 fatality rate may go down as more people are diagnosed with milder cases though (or it may go up or stay the same ... things can evolve rapidly!). For more information on COVID-19 effects, see our research breakdown.
3. Incubation period
The incubation period of the virus has been reported as 2-14 days, with a median of 5-6 days. One case study suggests that the incubation period could extend out to 24 days, although that hasn’t been verified widely.[10][11] That means you can be infected for quite a while and not feel sick. Thus, it’s important to always practice frequent handwashing and other transmission-reducing habits, and also have healthy sleeping and eating habits even if you don’t feel sick.
4. Viral load
If you have a harmful virus in your body, it's important to minimize how much is there. "Viral load" is basically how much virus there is per volume of a fluid (like blood, or the phlegmy stuff at the back of your throat called 'sputum'). For COVID-19, viral load appears to peak at around 5-6 days after symptoms start. Those without symptoms can also have have a significant viral load, which suggests that the virus can be spread before a person becomes symptomatic.[12]
Minimizing your exposure to the virus in order to reduce viral load is important, through measures including avoiding sick people when possible, frequent handwashing for 20 or more seconds, and avoiding touching your mouth/nose/eyes.[1][2] Studies suggest only around 5% of people wash their hands long enough (20 seconds) to kill infection-causing germs.[3]
Coronaviruses are among the "enveloped viruses", which have a lipid coating with spikes that allow easier binding to target tissues. This coating makes coronaviruses more susceptible to disinfectants, including alcohol-based hand sanitizers and wipes, than uncoated viruses are. While hand sanitizers have some efficacy,[13] less virus is removed than by thorough handwashing, due to the friction produced by rubbing your hands along with water pouring over them to wash away unwanted critters.[14][15]
COVID-19 is the infectious disease caused by the SARS-CoV-2 virus. It's alarming because it has a much higher fatality rate than the flu, and has spread more widely than previous coronaviruses. The incubation period is also quite long. Tried and true methods like frequent handwashing are essential. Our research breakdown has further coverage of recent COVID-19 studies.
Can you reduce risk through supplements or nutrition?
Supplementation
Nobody knows how well cold/flu supplement trials apply to coronavirus. The novel virus is too new, and is not structurally the same as either influenza or the various cold viruses.
That being said, there are a few supplements that have decent evidence for cold and flu. This page contains a more fleshed out evidence breakdown, but in short they are:
Moderate evidence:
- Vitamin C for reducing symptom duration if you're already using it regularly, especially for older people and athletes.[16][17][18][19]
- Vitamin D to help prevent upper respiratory infections.[20][21][22][23] Spending a long time indoors during winter is tied to seasonal flu through lower vitamin D, higher flu transmission in closed areas, and a lack of solar UV rays inactivating the virus.[24][25]
- Zinc oral lozenges to reduce symptoms, due to inhibiting viral replication at the back of your throat.[26][27][28]. Zinc spray may cause permanant side effects and swallowed tablets aren't effective.[29] Zinc acetate lozenges may be a bit more effective than zinc gluconate lozenges, although perhaps not significantly so.[28]
Preliminary evidence:
- Garlic has many more antibacterial studies than antiviral studies.[30][31] Evidence for prevention of the common cold (not treatment) is limited.[32]
- Echinacea, although the benefit shown is very small.[33][34]
- Elderberry, although very few studies exist thus far.[35][36]
- Pelargonium sidoides also has few studies, and only on treatment, with none on prevention.[37][38]
- Probiotics aren't one monolothic thing. Certain specific strains may help with prevention, although evidence is mixed, and efficacy may vary greatly by person due to gut microbiome individuality.[39][40][41][42]
- N-Acetylcysteine (otherwise known as NAC) has limited evidence for reducing flu episodes,[43] and a combination of L-Cystine and L-Theanine has limited evidence for reducing episodes of the common cold.[44]. Note that NAC has evidence for tumor initiation in animals when used regularly at high doses.[45][46][47] Supplements aren't automatically safe just because they're available without a prescription ... buyer beware!
Nobody knows how well supplement evidence (for prevention and symptom reduction of cold or flu) applies to COVID-19. A limited number of supplements have multiple, large, well-conducted randomized trials supporting their use. Most have fewer or smaller trials, often of weaker methodology. Supplements may also vary in potency by brand, and have unstudied or understudied dangers.
Nutrition and lifestyle interventions
A poor diet is tied to increased infection risk. Possibly a greater factor, though, is lack of sleep. Yet there are way more trials on supplements for infection prevention and treatment than there are for most dietary and lifestyle strategies. Don't be fooled! There's greater financial incentive to run supplement trials, and they are much cheaper, shorter, and easier to conduct than diet trials.
Moderate evidence:
- Sleep - Low sleep is increases suceptibility to be the flu and common cold[48], and generally messes with your immune system.[49]
- Less ultraprocessed food - High amounts of processed sugar and fat can interfere with proper immune function.[50] Even short-term hyperglycemia can impact response to infection.[51]
Very weak, preliminary evidence:
- Gargling - A small number of trials suggest some benefit.[52][53]
- Honey - Non-trial (cell) evidence suggests anti-influenza properties,[54] but there's no human trial evidence on this. Relatively stronger evidence indicates that honey may benefit coughs, though.[55][53][56]
There are far fewer trials for nutrition/diet and lifestyle interventions than there are for supplements, because it's much harder and more expensive to conduct trials. Getting sufficient sleep is probably the most critical strategy. It's likely that a diet high in ultra-processed foods could impact immunity through high amounts of processed carbohydrates and refined fats.