This means that as many as 400,000 people in the country could have already been infected with the virus.
The shock figure, which draws on analysis of blood donors in the country, was included in a status report published on Tuesday by the Danish Health Authority.
“There is a lot of contagion in Danish society, and there is a huge dark figure,” Kåre Mølbak, the agency's head, told the Berlingske newspaper.
“In the blood donor studies that have been done, you can see that maybe 70 times more people have had the infection than we can see in the statistics.”
A study of 1,000 blood donations given between April 1 and April 3 found that 3.5 percent had been infected with the virus, which would indicate that 65,000 people had probably already been infected by March 26.
SSI's estimate also drew on studies made in Germany and Iceland.