“You can see similar plumes exhaled from our nose and mouth, and how the airflow can be inhaled and exchanged between the two of us,” said Dr. Tang. “In a pub, bar or restaurant, if you’re sitting close enough to someone to smell their breath (garlic, curry or alcohol), you could be inhaling any exhaled virus, so this would be too close.”
Bars also tend to play loud music, which can prompt people to move closer together to talk, increasing risk for infection. “Bars have music, and you need to speak louder in order to be heard,” said Erin Bromage, a comparative immunologist and biology professor at the University of Massachusetts, Dartmouth. “You can’t social distance when it’s loud, and you need to move closer to hear a person.”
Dr. Bromage said he has advised bars trying to reopen that even if they move outdoors, they still should keep music levels very low. While quiet music changes the atmosphere, it also allows people to socialize without yelling and getting too close to each other’s faces.
Loud speech can be more risky for viral exposure than normal speech. Last year the journal Scientific Reports, published by Nature, reported that particle emission increases with the amplitude of speech. A person speaking quietly emits about six particles per second, while loud talking (without yelling) emits 53 particles per second. If a person has coronavirus, loud speech would increase the number of emitted particles and the risk of infecting another person nearby.
A spike in cases in South Korea shows the risks that barhopping can pose. In May, a 29-year-old man visited five bars and clubs in Itaewon, one of Seoul’s most popular nightlife districts. He later tested positive for coronavirus, and public health authorities have linked him to more than 100 cases of infection.
Another factor that makes bars so risky is alcohol. When people drink, they can forget that coronavirus is even a worry. “Alcohol of course can disinhibit people and perhaps promote even more breaches of social distance and sharing of drinks and food,” said Dr. Bitton.