The shocking death last year of thousands of tonnes of Iraq's freshwater carp was caused by a strain of herpes harmless to humans, the United Nations said on Wednesday. Iraqi fish farmers south of Baghdad were left reeling in late 2018 when they woke to find large sections of the Euphrates river surface <a href="https://www.thenational.ae/world/mena/iraq-opens-investigation-into-thousands-of-dead-carp-in-euphrates-river-1.787956">covered in waves of dead, floating carp</a>. The Ministry of Health issued a warning urging people not to buy or consume fish – for weeks Iraqis longed for their national dish, Masgoof, carp cooked over a wood-fire. Iraqi politicians quickly moved the issue to the top of the agenda, as rumours swirled over whether the fish were sick or the river had been poisoned. Deeming it a national security issue, Iraq’s newly appointed Prime Minister, Adel Abdul Mahdi, immediately assembled a crisis team led by the Ministry of Health and Environment and the Ministry of Agriculture to investigate its causes and take appropriate measures. “The scale of the fish kill was so huge, we had excavators working for four days clearing the fish from the river,” said Dr Ala Alwan, Iraq’s Minister of Health and Environment, who personally inspected the situation on the ground once news of the incident broke out in November. “We also used oil spill booms to contain and prevent the fish from drifting downstream,” he added. Other officials blamed cage overcrowding in Iraq's multi-million dollar aquaculture industry. But on Wednesday, the United Nations Environment Programme put the months-long international investigation to rest and pinned down source: the Koi Herpes Virus. "KHV is a very serious and lethal disease that is known to cause almost 100 per cent mortality rates in carps," said Dr Thomas Wahli, who heads the Swiss Reference Laboratory for Notifiable Diseases. The mass deaths in the fish farms of Saddat Al Hindiyah in Babylon province, about 80 kilometres south of Baghdad, caused panic among carp farmers, who said they lost thousands of dollars overnight. The mass-death was a blow to an industry once earmarked by USAID to be potentially worth over $90 million (Dh331ml) Samples of the dead fish, water, sediment and feed were sent to Dr Wahli's lab as well as facilities in Jordan and Italy. They confirmed the carp were killed by the viral outbreak, which does not pose a threat to humans, the UN said. Temperatures in the Euphrates dropped to around 24 degrees Celsius in November, a prime environment for fish-specific herpes. The overstocking of fish farms and low-quality river water may have also spread the disease further, the UN said in a statement. Iraq produces 29,000 tonnes of fish each year, according to 2016 statistics gathered by the UN Food and Agriculture Organisation. "This is the first case of Koi Herpes Virus disease in Iraq, and it is a significant case report which will need to be notified to the World Organisation for Animal Health," said Dr Alwan. "We are pleased to have been able to get to the bottom of this difficult case."