According to the research Ars Technica referenced, digital contact tracing doesn't start becoming effective at 60% - at 60% usage, digital contact tracing

According to the research Ars Technica referenced, digital contact tracing doesn't start becoming effective at 60% - at 60% usage, digital contact tracing can stop the pandemic There's no silver bullet with this virus. Contact tracing has proven ineffective in Singapore [1], even with additional layers of surveillance and thousands of dedicated staff reviewing CCTV footage, cell tower location data, and calling those suspected exposed to confirmed cases. https://www.economist.com/asia/2020/04/11/not-even-singapore-has-been-able-to-avoid-a-lockdown https://www.economist.com/asia/2020/04/11/not-even-singapore... All the while efficient contact-tracing teams—including members of the police and the army—identified and isolated thousands of people possibly infected with the virus. Members of the armed forces have been making up to 2,000 calls a day to hunt for potential carriers. Those told to stay at home for 14 days have been monitored assiduously to ensure compliance. (Unco-operative types face prosecution or the loss of their residency rights, if they are not citizens.) Yet in spite of everything, the virus continues to spread. Singapore’s approach continues to evolve. Take face masks. Initially Singaporeans were advised that they did not need to wear them unless unwell. Then on April 3rd, in his third televised address on covid-19, Lee Hsien Loong, the prime minister, said that the government would no longer discourage their use and would, in fact, distribute reusable ones to every household. Singapore’s testing regime may alter too. Currently people’s travel history and symptoms are among the factors considered before they are tested for the coronavirus. But health officials say the approach is reviewed regularly and that wider testing might be adopted in future. The difficulty with SARS-CoV-2 is once exposed, there's a window of several days of asymptomatic contagious transmissions. This is a biological health problem, and an app won't stop the spread. Viral fomites are like dust particles, airborne and remaining infectious on surfaces for upwards of 1-9 days depending on environmental factors [2]. Epidemiologists have predicted a global pandemic would happen sooner or later [3], and without a safe treatment the most effective action is to use Non-Pharmaceutical Interventions in any region where the virus might spread. Obviously due to modern air travel, it's now nearly everywhere. [1] https://www.economist.com/asia/2020/04/11/not-even-singapore-has-been-able-to-avoid-a-lockdown https://www.economist.com/asia/2020/04/11/not-even-singapore... [2] https://news.llu.edu/health-wellness/covid-19-virus-remains-active-some-surfaces-longer-than-previously-thought https://news.llu.edu/health-wellness/covid-19-virus-remains-... [3] https://wwwnc.cdc.gov/eid/article/26/5/19-0995_article https://wwwnc.cdc.gov/eid/article/26/5/19-0995_article https://stacks.cdc.gov/view/cdc/11425 https://stacks.cdc.gov/view/cdc/11425 https://stacks.cdc.gov/view/cdc/45220 https://stacks.cdc.gov/view/cdc/45220 https://cme-mec.ca/wp-content/uploads/2020/03/CME_Pandemic_Guide_Eng_2009Final.pdf https://cme-mec.ca/wp-content/uploads/2020/03/CME_Pandemic_G... https://www.ecdc.europa.eu/sites/portal/files/documents/Guide-to-pandemic-preparedness-revised.pdf https://www.ecdc.europa.eu/sites/portal/files/documents/Guid...