Why care for indoor air?

Outbreak on a bus

The bus, China

Chinese authorities and researchers from US universities have analyzed an outbreak of two buses that drove tourists to a Buddhist ceremony in Zhejiang, China.

Let’s take a closer look at the conditions


The passengers had travelled to the ceremony in two different buses. The vehicles were full, with scarcely 75 centimeters between rows. The journey took a total of 100 minuter – 50 minutes each way.



Patient 0, a 64-year-old woman, had been in contact with people from Wuhan. She had no symptoms until the following day.


In total, 23 people got infected on the bus. No one became ill on the other bus, despite the fact they were all mixing at the ceremony.


The air conditioning was on recirculation mode. The researchers believe that this was key; the passengers became infected regardless of their distance from Patient 0.


“Patient 0 in this outbreak appears to have been a superspreader,” explains Emily Gurley, an epidemiologist at Johns Hopkins University. “As at the restaurant, transmission could be explained by aerosols and droplets traveling longer distances due to the draft from the window or the air conditioning,” she adds.

A number of studies in Japan and elsewhere show that public transportation is not responsible for multiple infections as long as users maintain the rules of hygiene and protection. Especially the use of masks that prevent infected individuals from releasing contagious droplets into the atmosphere, as happened with patient 0 on the bus. It is also suggested that specific protection measures be introduced for drivers of public transportation, as well as improving ventilation and increasing the regularity of buses and trains in order to reduce crowding.

How can we minimise spread of infection in public transportation? 

  • Use face masks 
  • Improve ventilation
  • Avoid recirculation of air 
  • Increase regularity of buses and trains to reduce crowding 

Links to similiar studies and analysis

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  1. El País, https://english.elpais.com/society/2020-10-28/a-room-a-bar-and-a-class-how-the-coronavirus-is-spread-through-the-air.htmlhttps://english.elpais.com/spanish_news/2020-06-17/an-analysis-of-three-covid-19-outbreaks-how-they-happened-and-how-they-can-be-avoided.html, Authors: Javier Salas (javier@esmateria.com), Mariano Zafra
  2. US Centers for Disease Control and Prevention, Centers for Disease Control and Prevention in Guangzhou and Hangzhou, The Johns Hopkins Center for Health Security, the Spanish National Research Council’s Institute of Environmental Assessment and Water Studies (IDAEA-CSIC), European Centre for Disease Prevention and Control, International Laboratory for Air Quality & Health (WHO, Queensland), and the government of South Korea.

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