Hong Kong University’s head of Public Health Laboratory Sciences, Professor Leo Poon, is an expert on novel coronaviruses and has served as a consultant for the UN’s Food and Agriculture Organization. Fortune interviewed Poon about the risk of food transmitting COVID-19 to humans.

Fortune: How much of a transmission risk does food pose?

Professor Leo Poon: We don’t know whether there’s a risk or not. So far there’s no clear, documented evidence to show that COVID-19 can be transmitted by contaminated food. We know there are some suspicious cases, like the outbreak in a market in Beijing in June, but is the food itself a source for infection? We don’t know. They found evidence of the virus there, but it could have been traces of a dead virus that simply contaminated the food so, so far, there’s no evidence. There is a risk, but there’s no evidence, and compared to other means of transmission, the risk from food is much lower.

Are some foods riskier than others? 

Frozen products are more a risk. [Editor’s note: See more on freezing food below.] Grains, for example, are not very risky because they are shipped at room temperature. At room temperature a virus can only survive on a contaminated surface for a few days so, by the time grains are shipped to the market, the virus should already be dead.

What steps can consumers take to lower the transmission risk posed by food? 

For the general public, the best thing to do is try to maintain good hand hygiene. Washing hands might help to reduce the risk of transmission when buying, for example, chicken in the market. At home, consumers might like to wash raw meat with water to reduce the amount of virus [if any] on the food and then wash their hands once they’ve finished preparing the meat. Maintaining hand hygiene would be the upmost importance.

Does cooking food kill the coronavirus?

Viruses are very sensitive to heat. If you cook food properly then even if there’s a possibility of an infectious virus inside, it should be inactivated by the heat. In tests we’ve found that COVID-19 loses its infectious quality if submitted to a temperature of 70 C. or 158 F. for five minutes. So properly cooked food should be safe for eating.

Does freezing food kill the coronavirus?

If you freeze COVID-19, there’s some evidence to suggest it can survive in frozen samples for quite some period of time.

The virus likes the cold. We did an experiment in the past that showed the virus can survive at least two weeks at 4 C. or 39.2 F. At below freezing, it could survive even longer than that. The virus basically likes cold but not heat.

Is there any evidence the coronavirus is spread by ingesting food? 

So far there’s no clear evidence to show humans can absorb the virus from consuming contaminated food. There is a risk but no one has assessed it properly yet. However, even so, the risk is much lower than other known transmission modes, such as human-to-human transmission through coughing.