Practicing good hand hygiene is the best way people can protect themselves from coronavirus during a flight, a medical expert specializing in air transport told CNBC.

David Powell, medical advisor at the International Air Transport Association (IATA), told CNBC the risk of catching any serious viral infection during a flight is "very low" as the air on planes is purified with surgical-grade filters.

However, he said the risk remained if passengers were close to somebody on board who was unwell during the journey.

"We know that this virus has spread in the vast majority of cases through close contact with someone who is unwell at the time," he explained to CNBC's "Capital Connection" on Wednesday. "So that risk is what remains, and there are simple things you can do to reduce that risk, but through the air supply the risk is low."

Powell said that amid the coronavirus crisis in China, the most crucial way to minimize exposure to the infection was to practice good hand hygiene.

"Respiratory viruses transmit mostly through droplet spread — which is coughing or sneezing on somebody — or in some cases by fomite spread, which means you contaminate a surface which another person then immediately touches," he explained. "So hand hygiene is the primary thing."

That means anyone worried about exposure should avoid touching their own face and frequently wash and dry their hands — or use alcohol-based hand sanitizer if they aren't able to access hand washing facilities.