# Asymptomatic infection rates **URL:** \ **Category:** The Quarantine Zone\ **Tags:** covid-quarantine\ **Created:** [April 5, 2020, 8:17pm UTC](https://boards.straightdope.com/t/asymptomatic-infection-rates/851145 "2020-04-05T20:17:16Z")\ **Posts on this page:** 1\ **Showing post:** 136
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 29, 2020, 2:45am UTC](https://boards.straightdope.com/t/asymptomatic-infection-rates/851145/136 "2020-05-29T02:45:39Z")
A few bits to share that I think justify updating this thread. 1. From _BMJ Thorax_ another [cruise ship study](https://thorax.bmj.com/content/early/2020/05/27/thoraxjnl-2020-215091). > [@](#): > > We describe what we believe is the first instance of complete COVID-19 testing of all passengers and crew on an isolated cruise ship during the current COVID-19 pandemic. Of the 217 passengers and crew on board, 128 tested positive for COVID-19 on reverse transcription–PCR (59%). Of the COVID-19-positive patients, 19% (24) were symptomatic; 6.2% (8) required medical evacuation; 3.1% (4) were intubated and ventilated; and the mortality was 0.8% (1). **The majority of COVID-19-positive patients were asymptomatic (81%, 104 patients)**. Bolding mine. These do seem to be truly asymptomatic rather than presymptomatic individuals, but I am not sure if that can be stated with complete confidence. Also unclear the age range of those on the ship … my WAG is that a cruise of the Antarctic Peninsula following “a route similar to that taken by the British explorer, Ernest Shackleton, in 1915–1917” _might_ have a different demographic than a Carnival Cruise. Also noted that antibody studies done during an acute phase were falsely negative but follow up testing in not reported. 2) [Wuhan](https://onlinelibrary.wiley.com/doi/10.1002/jmv.25904). Population 11M. Workers required to be tested before being able to return to work. Very useful as this study was done not during a rapid rate of rise. Studies done while a population is on the curve are problematic as antibody positivity lags infection by 2 weeks or more. > [@](#): > > 50,008 confirmed cases and 2,579 deaths were from Wuhan … people have been allowed to resume working since April 8 if meeting a set of COVID-19-associated tests including SARS-CoV-2 nucleic acid test (NAT) of nasopharyngeal swabs, chest CT scan or a SARS-CoV-2-specific serological test. … there were 98 (98/1,021, 9.60%) from resuming group that were IgG positive and IgM and NAT negative. None of these people had a history of COVID-19, or suspect symptoms. These IgG+IgM-NAT- individuals with no history of COVID-19 probably suggested a recovered asymptomatic SARS-CoV-2 infection. … If one assumes that the 9.6% with past asymptomatic rate that means the true number of infected individuals in Wuhan was about 1.1M and the death rate (using the number quoted in the article) was 2,579/1,100,000 = 0.2%. Double it for assumed under-reporting of deaths maybe? Asymptomatic infections are being reported as 21 times more than “confirmed cases.” 3) [Spain](https://www.lamoncloa.gob.es/serviciosdeprensa/notasprensa/sanidad14/Documents/2020/130520-ENE-COVID_Informe1.pdf) study done 4/27 to 5/11. Information from reading the tables put into a Google translator and doing some simple calculations (40202 asymptomatic of which 2.5% were positive, so on). Positive IgG in: 1005 asymptomatic individuals, 46% of all who were positive; 568 with 1 to 2 symptoms, 26%; so on. Very few had been confirmed by PCR infections (247 of the over 60K). Overall > [@](#): > > The estimated prevalence of IgG antibodies against SARS-Cov2 in Spain is 5.0% (95% CI: 4.7% -5.4%), being very similar in men and women (5.0% (95% CI: 4.6% -5.4%) versus 5.1% (95% CI: 4.7%).In relation to age, the prevalence is lower in babies, children and young people, remaining quite stable in older age groups. > > The proportion of positives is higher in residents of large cities (\> 100,000 inhabitants) 6.4% (CI95%: 5.8-7.1) Using 5% with a deaths/million at the same time of about 530/million (0.05%) and IFR was running, very crudely about 1%. 4) [England.](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/888254/COVID19_Epidemiological_Summary_w22_Final.pdf)(Page 22.) Current week is week 22. > [@](#): > > … After making adjustments based on the latest information on the accuracy of the assay\*, the overall adjusted prevalence in London increased from 1.3% in week 13 to 10.6% in weeks 15-16 and 14.8% in week 18. … Given that the antibody response takes at least two weeks to become detectable, those displaying a positive result in week 18 are likely to have become infected before mid-April … Mid-April numbers for confirmed cases was about 1500/million (0.15%) and total deaths 2 weeks later (presumptively from infections up to that date) about 327/million (0.03%). Plugging in that’s 99 times more infected than confirmed cases and an IFR of 0.2%. 5) [Sweden.](https://www.folkhalsomyndigheten.se/nyheter-och-press/nyhetsarkiv/2020/maj/forsta-resultaten-fran-pagaende-undersokning-av-antikroppar-for-covid-19-virus/) > [@](#): > > The Public Health Authority has launched a survey to measure and estimate how many in the community have had covid-19. Blood samples are collected from laboratories in clinical chemistry and clinical immunology in nine regions: Jämtland, Jönköping, Kalmar, Skåne, Stockholm, Uppsala, Västerbotten, Västra Götaland and Örebro. > > The collection takes place during eight weeks in the spring of 2020. A total of 1,200 samples are collected each week for analysis of antibodies. Antibodies show that the immune system recognizes the SARS-CoV-2 virus. > > The analyzes for week 18 (a total of 1,104 analyzed samples) show, as expected, the largest proportion of positive antibody tests in Stockholm. A total of 7.3 percent of the blood samples collected from people in Stockholm were positive in the antibody study, which can be compared with a total of 4.2 percent in Skåne and 3.7 percent in Västra Götaland. > > The numbers reflect the state of the epidemic earlier in April, as it takes a few weeks for the body’s immune system to develop antibodies. > > Regarding age differences, the results show that it was most common with antibodies to covid-19 among people between 20 and 64 years. In total, 6.7 percent of the samples in this group were positive, which can be compared with 4.7 percent in the age group 0-19 years and 2.7 percent in the age group 65-95 years. Confirmed cases in Sweden in mid April about 1200/million (0.12%) and deaths 2 weeks later about 250/million (0.025%). About 59 times more with evidence of infection than confirmed infections and an implied IFR of 0.3%. FWIW. --- _[View the full topic](https://boards.straightdope.com/t/asymptomatic-infection-rates/851145)._