More than 8000 people have now been infected with the coronavirus in Iran and nearly 300 people have died, according to the country's health ministry.
That makes it one of the deadliest outbreaks outside China, just behind Italy where about 460 people have died.
But experts fear Iran may be under-reporting its cases and potentially tens of thousands more have been affected. So here's what we know about the outbreak so far.
On Tuesday night, Iran's health ministry announced at least 8,040 people had been infected with the COVID-19 virus and 291 people had died.
Around 30 Iranian officials are among those infected and several have died, according to media reports.
The infected include Masoumeh Ebtekar, one of Iran's 11 vice-presidents, and the deputy health minister, Iraj Harirchi. The dead include a senior adviser to Iran's supreme leader, Ayatollah Ali Khamenei, a politician, a high-ranking cleric, and diplomats.
All of Iran's 31 provinces have been hit by the virus, with the most cases in Tehran, followed by the Shiite pilgrimage city of Qom, and Mazandaran, a popular tourist spot in the north.
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Schools and universities have been shut down across the country and the public is being urged to stay at home.
Some hotels have also been closed in an effort to discourage travel, though the government is yet to officially impose quarantines.
WHY DO EXPERTS SAY THE NUMBERS COULD BE HIGHER?
Experts believe Iran may have initially lied about its number of cases and downplayed the severity of its outbreak to avoid impacting turnout at its recent parliamentary elections on February 21.
Some Iranian officials, for example, accused enemies such as the United States of exaggerating the risks in an attempt to keep voters away from the polls.
"The trust in the government was low after its brutal suppression of the protests in November and its cover-up of the accidental shooting-down of a Ukrainian jetliner in the aftermath of general Qassem Soleimani's assassination," Iranian health-policy experts Kamiar Alaei and Arash Alaei explained in a piece for the New York Times last week.
"A high turnout in the elections would help improve the legitimacy of the government. Tehran seems to have suppressed information about the coronavirus because it did not want participation in the elections to be affected."
HOW HIGH COULD THE NUMBERS BE?
Estimates vary, but Canadian researchers say the total number of infected could be in the hundreds of thousands considering how many cases it has exported across the world despite limited air travel links to other countries.
A journalist for The Atlantic has also suggested it could be in the millions after considering multiple different scenarios.
In one of the more modest scenarios, Graeme Wood explained: "A government website invited Iranians to submit details of symptoms they were experiencing. After 2 million responses, about 9 per cent reported COVID-19 symptoms.
"In the United States, among those whose symptoms and history have led them to be tested for COVID-19, about 10 per cent have eventually tested positive. If that rate holds, Iran would have 730,000 cases."
WHAT HAS THE WORLD HEALTH ORGANISATION SAID?
The World Health Organisation (WHO) sent a team of experts to Iran last week to help review and boost the country's response efforts.
On Sunday, the organisation's director of emergency operations, Richard Brennan, said he was impressed by what he'd seen.
"Very impressed by the dedication and hard work of the doctors and nurses and health workers here in Qom. The people of Qom should be very proud of their health workers," he said, wearing a face mask.
"I think we've seen very good care of the patients in hospital. We've seen good efforts at educating the population."