Tea has been known throughout the centuries to improve health, and studies show that it can potentially help you recover more quickly from a virus such as coronavirus. This is by no means a suggestion that it is a "cure". In fact the virus lives in your respiratory tract, not your digestive tract so what we drink or eat won't have much of an effect after the virus passes out of your nose/mouth. However, much like using hand sanitizer and covering your mouth, it is another weapon in our toolbox for preventing illness, and recovering more quickly if we do get it.
The word "corona" in coronavirus simply refers to the shape of the virus, of which there are many including SARS and MERS. This article shares a bit of history and a visual schematic about coronaviruses. Coronaviruses are positive-sense single-stranded RNA viruses (+ssRNA), RNA meaning that they have a ribonucleic acid as their genetic material... actually so is the common cold. Wikipedia has a great description of RNA viruses.
We need to know these basic facts to understand whether studies and articles pertain to coronavirus specifically. But it is well known that all viruses can be killed by applying a certain amount of heat for a certain period of time.
Extremely hot temperatures kill viruses by using heat to damage cell structure after prolonged exposure. Different viruses have different heat thresholds at which point they die. According to this article, the novel coronavirus is killed at water 56C or higher (130F) for 30 minutes. Of course our body can never get that hot, but that is about as hot as something that came right off of a buffet. It's your tea or coffee after about 5 minutes of cooling down. The virus will ultimately find its best home in your respiratory tract, not digestive, but sipping a hot beverage may be preventive.
EGCG, formally known as epigallocatechin gallate, is a plant-based compound. Much of the reason why research says green tea is good for you is credited typically to its high EGCG content. Now consider this journal article stating that "Studies have shown that GTCs [green tea catechins], especially epigallocatechin-3-gallate (EGCG) have antiviral effects against diverse viruses." It goes on to show a chart summarizing the inhibitory effects of EGCG on various viruses by green tea catechins. I will list below only those that refer to +ssRNA viruses:
Docking into the binding pocket of E protein. Destruction of the virus particle by interacting with the lipid envelope
Blocking entry into target cells
Suppressing virus gene expression
Interference with virus adsorption
Inhibition of production of progeny virus by reducing regeneration
Inhibition of viral adsorption and cell intrusion of PRRSV by EGCG palmitate
Do you know what all of that means? I don't either. But it definitely sounds like something I want happening in my body if I get a virus.
Green tea has the highest levels of EGCG while oolong and black have significantly less because they are either partially or fully oxidized. From a cup of green tea, you can expect to consume about 20-40 mg; from a cup of matcha maybe 50-60 mg.
Without knowing exactly how much EGCG was needed to have the effects described above in the journal article, I can tell you that generally speaking, it's going to be at least 300mg. More than 800mg in a day can have negative health consequences. So if you're committed to getting these benefits, figure 10 cups per day.
One interesting piece of research that has surfaced about coronaviruses was published many years ago discussing the effect that zinc has on coronaviruses. This research states that zinc can efficiently impair the replication of a variety of RNA viruses.
Teas with the highest zinc content are dandelion, rose hips, chamomile and nettle. Rooibos is known to contain traces of zinc, as do green and black tea.
Knowing what I know now, I'm going to more or less always have a cup of warm green tea. Rather than steeping the leaves and then removing them, I will be leaving the leaves in my cup to continue to brew, and topping myself off with hot water once or twice before discarding and starting over. Some green teas get very bitter this way, but I've found that Genmaicha Matcha is wonderful for this use. And containing both green tea leaves and matcha, it maximizes my EGCG intake.
And at night, I'll be savoring an extra cup of chamomile tea at night.