By Benoit Faucon, Sune Engel Rasmussen and Jeremy Page 

Iranian officials trace the origins of the country's coronavirus epidemic to the holy city of Qom, home to dozens of seminaries and religious shrines -- but also a number of Chinese-backed infrastructure projects built by scores of workers and technicians from China.

This critical link to China, centered in Qom, has helped keep Iran's economy alive in the face of American sanctions. And it is now being stress-tested by the coronavirus. The exact route of the virus is unclear. But Iran's strategic partnership with Beijing has created a constellation of potential contacts that helped unleash the illness, called Covid-19.

"China has been the trading partner of last resort but, in this case, it has turned into a very toxic bomb," said Sanam Vakil, deputy Middle East director at Chatham House, a think tank in London.

China Railway Engineering Corp. is building a $2.7 billion high-speed rail line through Qom. Chinese technicians have been helping refurbish a nuclear-power plant nearby. There are also Chinese religious students studying at Qom's seminaries.

Iranian health officials have said the source of the outbreak is likely either Chinese workers in Qom or an Iranian businessman from Qom who travelled to China. Iranian officials haven't identified the businessman by name but say he travelled from China to Qom through an indirect flight.

Once the pathogen was loose in Qom, a city of roughly one million people, it spread rapidly, taxing a sanctions-stretched health-care system, amplifying economic woes and fueling an anti-Chinese backlash.

"We were unhappy with all these crappy Chinese goods everywhere," said a housewife who asked to be quoted by her last name, Ms. Ashtari. "Now they brought us this crappy virus, too."

According to official statistics, more than 350 Iranians have died from the new virus. The government says 9,000 people have been infected; epidemiologists say the number could actually be in the tens of thousands. Travellers, many of them pilgrims, carried the virus to at least 15 other countries, the World Health Organization and governments in those countries say.

Dozens of Iranian officials and parliamentarians have contracted the coronavirus since the outbreak began in Iran. Iranian media Wednesday evening reported that First Vice President Eshaq Jahangiri had contracted the coronavirus, along with two other cabinet members. The semiofficial Fars news agency published a list of 24 officials infected with the virus, at the top of which was Mr. Jahangiri. On the list were also the minister of industry, mines and business, Reza Rahmani, and the minister of cultural heritage, Ali Asghar Mounesan.

Mr. Jahangiri is the most senior Iranian official to contract the virus yet. The list of infected officials also counts more than 20 lawmakers, as well as Masoumeh Ebtekar, a spokesperson for the Iranian students that besieged the U.S. Embassy in Tehran in 1979 and who currently serves as a more junior vice president and the highest-ranking Iranian woman in government. Deputy Health Minister Iraj Harirchi, prominent reformist Mahmoud Sadeghi and the head of parliament's foreign policy commission Mojtaba Zonnouri have also been infected.

The government reacted slowly to the outbreak. Hours after the first infections were announced, the victims were declared dead, suggesting that the coronavirus had been allowed to spread for weeks.

For days after the first cases were discovered on Feb. 19, Qom's clerics defied government orders to close shrines. By the end of the month, when authorities cancelled Friday prayers for the first time in decades in an effort to stem the epidemic, the disease had already spread to most provinces.

Weeks earlier, on Feb. 1, as the coronavirus outbreak centered on the central Chinese city Wuhan worsened, the Iranian government had banned its airlines from flying to China. It gave an exception, however, to Mahan Air, which has emerged as a popular source of air transport for the country's powerful Islamic Revolutionary Guard Corps.

The U.S. government alleges the airline transported personnel, money and arms for the Guards, and provided transportation for the Lebanese Hezbollah militia, which Washington considers a terrorist organization. After the Guards' Qods Force commander Qassem Soleimani, who frequently travelled with the airline, was killed by a U.S. drone in January, his coffin was returned to Iran on a Mahan Air flight.

Mahan Air said in a statement to The Wall Street Journal that it had carried out eight flights between Tehran and China between Feb. 1 and Feb. 9 to transfer Chinese and Iranian passengers to their respective home countries. Since February 12, the airline had flown 12 flights with cargo -- such as flying testing kits and disposable masks to Iran -- and followed disinfection and hygiene instructions issued by the health ministry.

"We carry out flights under full supervision of the health ministry," Reza Jafarzadeh, spokesman of Iran's Civil Aviation Organization, told state radio. "Whether incoming foreign passengers have been tested or not is a matter for the health ministry."

Mahan Air has made at least 43 trips since Feb. 1, according to online flight records from FlightRadar24, including one to Wuhan on Feb. 5, which evacuated 70 Iranian students living there, according to Iran's Foreign Ministry. The students were quarantined after their arrival from Wuhan, deputy health minister Alireza Raeisi was quoted as saying by the official Islamic Republic News Agency. Mahan Air said the numbers from the flight tracker are inaccurate.

Mahan Air's most recent flight from China landed in Tehran from Shanghai on the morning of March 9, according to FlightRadar24. There is no official total count of passengers.

Iran's Minister for Roads and Urban Development said Thursday that an investigation by the health ministry had concluded that the coronavirus hadn't been brought to Iran by one of the country's own airlines, according to state television. The minister didn't provide an explanation for that conclusion.

Irate Iranians have accused the airline of serving as a conduit for the deadly virus. "We won't forget the coronavirus of the traitor company #Mahan Air," said one Twitter user, while another called on the airline's managers to be prosecuted.

To combat the epidemic, Iran's authorities have erected checkpoints on roads leading to and from major cities, and Revolutionary Guard and police forces on Friday closed streets leading to major infection hubs in the country's north, far from Qom. Drones have been deployed to disinfect streets.

In contrast to China, which took draconian measures to contain the coronavirus in Wuhan, Iranian officials have insisted they won't quarantine Qom, calling such measures a relic from pre-World War 1 times.

Iran's health-care system has struggled to cope with the sudden case load stemming from keeping the extent of the illness under wraps, according to Kamiar Alaei, an Iranian public-health expert and co-president of the Institute for International Health and Education in Albany, N.Y. "It's not necessarily about the quality of the health-care system," he said. "It's about mismanagement and misinformation."

On March 5 -- two weeks after the first deaths occurred in Iran -- the commander of the Islamic Revolutionary Guard Corps, Maj. Gen. Hossein Salami, suggested that the global spread of the coronavirus may be the work of U.S. biological warfare against China and Iran: "Today, the country is engaged in a biological battle," Mr. Salami said at a ceremony in Kerman.

Many Iranians have refused to get tested, worried that they might contract the virus in hospital.

China, Russia and the World Health Organization have delivered thousands of test and diagnostic kits as well as respiratory machines. France, Germany and Britain also have transported equipment and pledged close to EUR5 million ($5.67 million) through the World Health Organization or other United Nations agencies.

But Iran officials, traders and experts say it won't be enough to make up for dwindling stocks of supplies and faulty equipment. Most of the installed equipment in hospitals in the country was historically supplied by Western companies, which Iranians have tended to prefer to Chinese alternatives.

Some companies that supply testing kits or respiratory equipment, such as ventilators, have stopped delivering to Tehran because their banks refuse to carry the payments, Iranian distributors said. In September, the U.S. imposed sanctions on Iran's central bank.

Despite Iran's own struggle to contain the virus, many Iranians are directing their anger at China for bringing the illness to their country in the first place. "When you put all your eggs in one basket, this is what you get," said Ali, a 43-year-old kitchenware seller in Tehran. "The Chinese are everywhere."

To keep a lid on popular anger, the government in late February blocked entry for Chinese travellers. China hasn't blocked entry for travellers from Iran, although Beijing and Shanghai have since early March required arrivals from Iran and others badly affected by the coronavirus to self-quarantine for 14 days. Three charter flights from Iran have brought hundreds of Chinese back to China.

In recent days, China announced that at least 42 people -- including some Chinese nationals who came back from Tehran via Moscow or Bangkok -- were found to be carrying the virus after returning from Iran.

--Drew Hinshaw, Aresu Eqbali and Lekai Liu contributed to this article.

Write to Benoit Faucon at benoit.faucon@wsj.com, Sune Engel Rasmussen at sune.rasmussen@wsj.com and Jeremy Page at jeremy.page@wsj.com

(END) Dow Jones Newswires

March 11, 2020 12:12 ET (16:12 GMT)