Expert on the number of infected in Spain: "not good for Sweden"

The study was conducted by the Carlos III Institute and the Spanish counterpart to Statistics Sweden and began in late April, reports the news agency Reuters and several media outlets.

90,000 people from 36,000 households were tested for antibodies, and according to preliminary results, about 5 percent of the total Spanish population has been infected.

The test examines the presence of so-called IgG antibodies, antibodies that take a long time to build up because they show that the test subject has had the infection but is no longer active, writes El País.

The same test also allows you to see if the person has IgM antibodies, which the body produces around the sixth or seventh day after the symptoms show up.

The results also showed that the spread of infection varied widely from region to region. In the metropolitan area of ​​Madrid, 11.3 percent of the population is estimated to have developed antibodies.

Tove Fall, epidemiologist at Uppsala University, is impressed by the Spanish study but fears that it may indicate that Sweden's strategy may be forced to re-evaluate.

- This is not good news for Sweden. Spain is one of the worst affected countries in the world and that they are at such low proportions of people who are estimated to be infected is not good, says Tove Fall in Aktuellt.

Fall says it is hoped that Sweden will already have a large proportion who have gone through the infection, but that the Spanish figures contradict it.

The hope that the herd immunity would be relatively high?

- Yes, or close. But this speaks to the fact that we would have come this far.

What could the herd immunity be like here?

- A survey in Belgium showed about six per cent and in Spain there were five, maybe somewhere around there because we have had fewer deaths than in those countries.

Tove Fall says that the Spanish survey is very important because so far there is no good scientific basis for how strategies should be formulated - and believes that this research can force countries to change methods.

- It is a very long way to go to reach Spain at 60 or 70 percent, and extremely high death rates. Maybe you have to work on trying to reduce the infection as much as possible until we find other ways.