All of my kids are home from college and we’re all trying to shelter in place, wipe down surfaces several times a day, and not share food in the same way. However, yesterday I found some leftovers in the fridge, but I couldn’t be sure if someone had snacked on these before. So I thought to myself, instead of eating this food cold, I should microwave it first to reduce the viral load if present. So let’s dig into whether I made the right decision and whether you should do the same.
How Does a Microwave Oven Work?
The microwave in your kitchen heats and cooks food by using electromagnetic radiation in the microwave frequency range. This energy causes the water molecules in the food to rotate and twist (see above). This produces heat.
Can Your Microwave at Home Kill Viruses?
The short answer is YES. In fact, there is research on using the microwave in your kitchen to kill lethal viruses like HIV (1). How much for how long?
First, there’s the power of your microwave. This is measured in watts. The higher the watts, the shorter the cooking time. The above study used a wattage of 800. The average microwave oven these days has a wattage of about 1,000 (from my review of what’s being sold on Google). It seems hard to buy a microwave with less than 700 watts, so yours likely has more than enough power.
Second, for how long do you need to cook? The above study observed the destruction of the virus at 2 minutes at 800 watts. So 2 minutes in the average microwave should be more than enough time.
How About Coronaviruses?
Another study looked at the coronavirus called IBV (Avian Coronavirus) and a kitchen microwave (wattage not reported but they noted that this was a kitchen model) (2). The researchers couldn’t isolate this coronavirus (meaning it was dead) with an exposure of as little as 5 seconds!
How Does this Work?
Viruses contain plenty of hydroxyl groups that vibrate as shown in the animation above. These produce heat. Most experts believe that it’s the heat that really kills the virus. However, the one study above that shows that 5 seconds works, may mean it’s more than the heat.
We know that the coronavirus is deactivated by heat (3). 56C (132 F) reduces the alive virus by 10,000 times by 15 minutes. Hotter temps will kill more virus more quickly. Hence, I would heat your food for 2 minutes or so, getting it boiling hot. For example, I was reheating chili which I microwaved for 2 minutes until I saw it begin to boil. I then took it out and cooled it off by stirring it which took a few minutes and then jumped in!
How About “Take Out” Food?
The restaurants are closed, but many are permitted to offer take out. The same rules apply here. One way you can enhance your safety is to focus on cooked take out. Get the hot stuff and stay away from the cold stuff.
The upshot? It looks like my instincts that microwaving the food was the best option were right. So in this time of leftovers and people sharing lots of food because restaurants are closed, nuke that meal!
(1) Siddharta A, Pfaender S, Malassa A, et al. Inactivation of HCV and HIV by microwave: a novel approach for prevention of virus transmission among people who inject drugs. Sci Rep. 2016;6:36619. Published 2016 Nov 18. doi:10.1038/srep36619
(2) Elhafi G, et al. Microwave or autoclave treatments destroy the infectivity of infectious bronchitis virus and avian pneumovirus but allow detection by reverse transcriptase-polymerase chain reaction. Avian Pathology (June 2004) 33(3), 303/306. https://doi.org/10.1080/0307945042000205874
(3) (3) World Health Organization. First data on stability and resistance of SARS coronavirus compiled by members of WHO laboratory network. https://www.who.int/csr/sars/survival_2003_05_04/en/ Accessed 3/21/20.