< Hygiene

Is spitting on the floor dangerous to others?

Text updated on 2020-06-02

Yes, because the SARS-CoV-2 coronavirus is concentrated in the saliva, and it may degrade more slowly there.

The saliva of infected persons contains high levels of SARS-CoV-2 coronavirus, and two cases of direct contamination by spitting in the face have been strongly suspected, in Victoria railway station in the United Kingdom.

Spitting on the floor of a public place could help spread the virus, via the soles of shoes, which can carry and disperse the particles, which become airborne again when they dry - but this has not yet been studied.

The coronavirus has poor heat resistance and does not survive long in outdoor environments. In sputum, it may degrade less quickly because the proteins and moisture in the saliva reduce the sensitivity of the virus to heat.

In many countries, spitting was banned in the last century to limit the spread of tuberculosis (in France, for example, by decree on March 22, 1942). Despite this, some people are used to spitting frequently, in the street and in other public places. The decontamination of pavements and sidewalks, sometimes carried out in certain cities, seems to be a disproportionate means of eliminating a virus that only survives for a few hours or even a few days.

Finally, in the city, avoid walking on what looks like spit and to take off your shoes when you get home to prevent the soles from contaminating the house.

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A large number of copies of the virus are found in the "cough" saliva collected by the patients themselves in Hong Kong. This number of virus drops during the course of the illness and then disappears 8-10 days after the first symptoms.

To, K. K. W., Tsang, O. T. Y., Yip, C. C. Y., Chan, K. H., Wu, T. C., Chan, J. M. C., ... & Lung, D. C. (2020). Consistent detection of 2019 novel coronavirus in saliva. Clinical Infectious Diseases.

In Melbourne, Australia, SARS-Cov-2 was detected in the saliva of 85% of PNP-positive patients by PNP testing. The number of RNA copies detected was lower in saliva than in the nasal swab. Finally, virus was detected in the saliva of one of the 50 PNP-negative patients. Despite a somewhat lower sensitivity in saliva, the authors of this Australian study support the generalization of saliva specimens because of their advantages.

Williams, E., Bond, K., Zhang, B., Putland, M., & Williamson, D. A. (2020). Saliva as a non-invasive specimen for detection of SARS-CoV-2. Journal of Clinical Microbiology.

Two cases of direct contamination by spitting in the face are suspected at Victoria station in the United Kingdom.

BBC News article of 12 May 2020.

French decree prohibiting spitting on the ground in public places.

Dated March 22, 1942.

Coronaviruses are sensitive to heat: SARS-Cov is inactivated within 30 min at 56°C. On the other hand, if 20% protein is added to the virus suspension, more than 20,000 viruses remain after 30 min at 56°C, and heating to 60°C is required to inactivate the virus suspension.

Rabenau, H. F., Cinatl, J., Morgenstern, B., Bauer, G., Preiser, W., & Doerr, H. W. (2005). Stability and inactivation of SARS coronavirus. Medical microbiology and immunology, 194(1-2), 1-6.

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