--- title: Study: Up to 80% of COVID-19 Infections Are Asymptomatic description: In a cruise ship COVID-19 outbreak, 80% of people who tested positive had no symptoms, showing the extent of asymptomatic transmission. canonical: https://time.com/5842669/coronavirus-asymptomatic-transmission/ author: Jamie Ducharme article:opinion: false article:content_tier: free article:published_time: 2020-05-27T22:30:07.000Z article:modified_time: 2026-08-04T07:52:07.075Z article:section: Health og:title: New Study Shows the Extent of Symptom-Free Coronavirus Spread og:description: 80% of people who tested positive were asymptomatic og:url: https://time.com/5842669/coronavirus-asymptomatic-transmission/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltf82a97950f28a39c/698a0e7f096a94ed246a8313/social-distancing-circles.jpg?branch=production&width=1024&quality=75&auto=webp&crop=16:9 og:image:width: 1024 og:image:height: 576 og:image:alt: San Francisco during social distancing og:type: article twitter:card: summary_large_image twitter:title: New Study Shows the Extent of Symptom-Free Coronavirus Spread twitter:description: 80% of people who tested positive were asymptomatic twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltf82a97950f28a39c/698a0e7f096a94ed246a8313/social-distancing-circles.jpg?branch=production&width=1024&quality=75&auto=webp&crop=16:9 ---  # Up to 80% of COVID-19 Infections Are Asymptomatic, a New Case Report Says > Sponsored content. 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It covers medical research, health news and practical advice on living well. #### Where can I get reliable health news by email? Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ## Video: FAQ: What are the Symptoms of COVID-19? [Watch (HLS stream): FAQ: What are the Symptoms of COVID-19?](https://cdn.jwplayer.com/manifests/HOy4QjLj.m3u8) (0:56)  _Published 2020-04-13. A World Health Organization report from February found that around 80% of patients with laboratory confirmed cases “have mild disease and recover.”_  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. May 27, 2020 10:30 PM UTC  An aerial view of people lying in social distancing circles at San Francisco's Dolores Park amid the coronavirus outbreak on May 24, 2020. An aerial view of people lying in social distancing circles at San Francisco's Dolores Park amid the coronavirus outbreak on May 24, 2020. Liu Guanguan/China News Service via Getty Images  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. May 27, 2020 10:30 PM UTC In one cruise-ship coronavirus outbreak, more than 80% of people who tested positive for COVID-19 did not show any symptoms of the disease, according to [a new paper](https://thorax.bmj.com/content/early/2020/05/27/thoraxjnl-2020-215091) published in the journal _Thorax_. The research shows just how prevalent asymptomatic transmission of COVID-19 may be—a reality that both suggests official case counts are drastic underestimates, and emphasizes the importance of [practicing social distancing](https://time.com/5835818/socializing-coronavirus-social-distancing/) even if you feel healthy. Researchers have known for months that asymptomatic transmission of COVID-19 is possible and common, but without [population-wide testing](https://time.com/5841111/san-francisco-universal-coronavirus-testing/), it’s been difficult to estimate how many people get infected without showing symptoms. The new paper provides an example of how widespread asymptomatic transmission can be, at least in a contained environment. The (unnamed) cruise ship in the new paper left Argentina in mid-March, with plans to travel around the Antarctic Peninsula and over to South Georgia Island in the south Atlantic ocean. All passengers were checked for coronavirus symptoms before departure, and people who had traveled through COVID-19 hotspots were not allowed on board. Even still, a passenger developed a fever eight days into the trip, triggering a ship-wide lockdown. Crew members and additional passengers began to develop coronavirus symptoms over the next few days. The ship was not allowed to re-dock in Argentina after the country closed its borders, so it continued on to Uruguay, where eight people were evacuated to a hospital. Uruguayan officials eventually arranged for everyone remaining on board to get tested before the boat docked. Out of 217 people on board, 128 tested positive for COVID-19—but only 24 of those people showed symptoms prior to testing. The remaining 104 people—81% of those who tested positive—had not experienced any symptoms, the researchers report. There were also 10 instances of people testing negative even when their cabin mate tested positive, which the authors say suggests there were some false-negative test results. It’s difficult to extrapolate the results to larger populations, since the people on board the ship were living in close quarters while entirely isolated from outside life for about a month. Even still, the results are a stark reminder of how likely COVID-19 is to spread within communities, and how difficult it can be to tell when it does. That’s a particularly important lesson to consider as [states reopen](https://time.com/5837846/us-states-fall-short-covid19-testing/) and nice weather [eats away at many people’s resolve](https://time.com/5829312/covid-19-caution-fatigue/) to stay home. The virus can and does spread undetected—and an asymptomatic case can still cause serious illness if it spreads to someone else. Until [a vaccine](https://time.com/5838282/coronavirus-vaccine-moderna-results/) is available, the safest way to keep coronavirus from spreading is to keep your distance from others, whether you’re sick or not. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/5842669/coronavirus-asymptomatic-transmission/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/5842669/coronavirus-asymptomatic-transmission/"},"headline":"Up to 80% of COVID-19 Infections Are Asymptomatic, a New Case Report Says","datePublished":"2020-05-27T22:30:07.000Z","dateModified":"2026-08-04T07:52:07.075Z","description":"In a cruise ship COVID-19 outbreak, 80% of people who tested positive had no symptoms, showing the extent of asymptomatic transmission.","url":"https://time.com/5842669/coronavirus-asymptomatic-transmission/","keywords":["COVID-19"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltf82a97950f28a39c/698a0e7f096a94ed246a8313/social-distancing-circles.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Jamie Ducharme","jobTitle":"Ducharme is a contributor to TIME.","url":"https://time.com/author/jamie-ducharme/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltf82a97950f28a39c/698a0e7f096a94ed246a8313/social-distancing-circles.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"San Francisco during social distancing","caption":"San Francisco during social distancing","creditText":"Liu Guanguan/China News Service via Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/covid-19/","name":"COVID-19"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/5842669/coronavirus-asymptomatic-transmission/","name":"Up to 80% of COVID-19 Infections Are Asymptomatic, a New Case Report Says"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"FAQ: What are the Symptoms of COVID-19?","description":"A World Health Organization report from February found that around 80% of patients with laboratory confirmed cases “have mild disease and recover.”","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/HOy4QjLj/poster.jpg?width=720","uploadDate":"2020-04-13T20:35:20.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/HOy4QjLj.m3u8","embedUrl":"https://time.com/5842669/coronavirus-asymptomatic-transmission/","duration":"PT56S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/5842669/coronavirus-asymptomatic-transmission/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```