Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • NEWS

Delta’s rise is fuelled by rampant spread from people who feel fine

People infected with the Delta variant generally do not have COVID-19 symptoms until two days after they start shedding the coronavirus.
  1. Smriti Mallapaty

    1. Smriti Mallapaty is a senior reporter in Sydney, Australia.

    View author publications

    You can also search for this author in PubMed  Google Scholar

A health worker takes a swab from a resident.

People in Qingdao, China, are tested for COVID-19.Credit: AFP via Getty

People infected with the Delta variant of SARS-CoV-2 are more likely to spread the virus before developing symptoms than are people infected with earlier versions, suggests a detailed analysis of an outbreak in Guangdong, China1.

“It is just tougher to stop,” says Benjamin Cowling, an epidemiologist at the University of Hong Kong and a co-author of the study, which was posted on a preprint server on 13 August.

Cowling and his colleagues analysed exhaustive test data from 101 people in Guangdong who were infected with Delta between May and June this year, and data from those individuals’ close contacts. They found that, on average, people began having symptoms 5.8 days after infection with Delta — 1.8 days after they first tested positive for viral RNA. That left almost two days for individuals to shed viral RNA before they showed any sign of COVID-19.

A dangerous window

An earlier study2 and an unpublished analysis by Cowling and others estimate that before Delta emerged, individuals infected with SARS-CoV-2 took an average of 6.3 days to develop symptoms and 5.5 days to test positive for viral RNA, leaving a narrower window of 0.8 days for oblivious viral shedding.

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

doi: https://doi.org/10.1038/d41586-021-02259-2

References

  1. Kang, M. et al. Preprint at medRxiv https://doi.org/10.1101/2021.08.12.21261991 (2021).

  2. Xin, H. et al. Clin. Inf. Dis. https://doi.org/10.1093/cid/ciab501 (2021).

    Article  Google Scholar 

Download references

Subjects

Latest on:

Nature Careers

Jobs

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing

Search

Advanced search

Quick links