Nearly one in five Iranians may have been infected with the novel coronavirus since the country's outbreak started in February, a health official said Tuesday.

"About 15 million Iranians may have experienced being infected with this virus since the outbreak began," said Ehsan Mostafavi, a member of the task force set up to combat COVID-19.

This meant the virus was "much less lethal than we or the world had anticipated", the semi-official ISNA news agency quoted him as saying. The figure represents 18.75 percent of the more than 80 million population of Iran, which on Tuesday announced another 74 deaths from the coronavirus.

Mostafavi said it was derived from serology tests to identify antibodies in patients who have recovered from the illness. These differ from polymerise chain reaction (PCR) tests, which detect the presence of an antigen. Iran says it has carried out more than one million PCR tests to "confirm" infections and report them so far.

Health ministry spokeswoman Sima Sadat Lari said 74 new coronavirus fatalities in the past 12 hours had raised the overall death toll to 8,425. Cases of infection rose by 2,095 over the same period to total 175,927, she added.

Lari replaced Kianoush Jahanpour as the health ministry's spokesperson on Tuesday, according to a ministry statement.

Health Minister Saeed Namaki called on her to "avoid politicisation" of issues and to coordinate with him "before making any remarks on social media or to the press," it added. Jahanpour had come under fire in March after saying China's reporting of its COVID-19 figures was a "bitter joke".

He was slammed on Twitter by the Chinese ambassador to Tehran, Chang Hua, and later retreated by praising Beijing for its support of Tehran during the pandemic. Iran-China relations are usually warm as Beijing is one of Tehran's top trade partners, especially in oil.