In English, the letters P, T, and K are aspirated, meaning that when spoken, numerous small droplets fly from the mouth of the speaker, into the air. In times of COVID-19, this matters: It means that casual conversation in English may be more likely to potentially spread the virus.
Suspicions that aspirated pronunciation may spread respiratory viruses date back at least 17 years, to a Lancet article that noted dramatically lower SARS rates in speakers of Japanese (with limited aspirated consonants) versus English.
This spring, researchers at Moscow’s RUDN University suspected that aspirated consonants may play a role in spreading the new coronavirus and compared COVID-19 rates in 26 countries to the frequency of aspirated consonants in those countries. The countries with aspirated consonants had 20% higher rates of COVID-19.