The double danger of a Covid-19 outbreak and deadly haemorrhagic fever cases has prompted the northwestern Chinese city of Xian to suspend school and start citywide coronavirus tests. All students from kindergarten to high school were ordered to stay home from Monday until further notice, local newspaper Huashang Daily reports. The city reported 21 Covid-19 cases on Sunday and one patient who has not yet shown symptoms, bringing the total number of infections in the current wave to 57. Local health authorities believe the outbreak was introduced on a flight from Pakistan on December 4, but so far the chain of transmission is unclear. More Covid-19 cases were discovered during testing, indicating community spread had occurred and the outbreak was still in the “rapid development” stage, according to Liu Feng, director of the Shaanxi Centre for Disease Control and Prevention. Genetic sequencing showed the outbreak, first reported on December 9, was linked to the flight from Pakistan on which six out of 180 passengers were infected. A staff member who disinfected the quarantine hotel rooms of infected passengers from the Pakistan flight became the first case in the local outbreak and five days later a colleague was also reported to be infected. Last Wednesday, an outbreak was detected at Changan University in Xian and was found to be spreading. Cases included one person who had been in the airport around the same time the Pakistan flight landed, sparking fears that the airport may have been contaminated. Two passengers who flew from Xian to Shenzhen on December 4 were confirmed by authorities in Dongguan , in the southern Guangdong province, to be infected and genome sequencing confirmed their infections as part of the Xian transmission chain. Omicron shows China got it right on Covid-19 strategy, top expert says On Sunday, a student in Beijing who flew from Xian on December 14 was found to have been infected, indicating the outbreak had spread farther. Xian Xianyang International Airport issued a notice on Sunday asking all passengers to present a negative coronavirus report within 48 hours to enter the terminal. Meanwhile, the city is also battling haemorrhagic fever as the local health agency calls for people to be vaccinated to prevent the disease. The city has seen numerous haemorrhagic fever cases this winter but has not publicly reported the number of infections or deaths. The disease is predominantly caused by hantavirus. Rodents are the main source of infection and it can be transmitted by a rodent bite or by eating food or water contaminated by a rodent. It transmits mostly from animal to people and spread from human to human is extremely rare. The Xian Centre for Disease Control and Prevention said in a statement on Sunday that haemorrhagic fever was currently at its peak. It said the disease’s early symptoms were similar to the onset of respiratory infectious diseases such as a common cold and the centre urged residents not to ignore symptoms or wait to be treated. The centre urged people from 16 to 60 years old – especially students who had recently turned 16 and farmers – to get vaccinated as soon as new vaccine stocks arrived in the city. The vaccination regimen requires the first two doses to be given 14 days apart and the third dose delivered a year later. Animals hunted, traded and homeless host twice as many viruses that infect us Data from the Chinese CDC website shows that the number and incidence of epidemic haemorrhagic fever in the country has fallen – from 11,966 cases and 97 deaths in 2018 to 8,121 cases and 48 deaths in 2020 – but in Shaanxi province cases rose. According to the Shaanxi CDC 2020 work report, a total of 1,834 cases of haemorrhagic fever were reported in the province last year, up 90.05 per cent from 965 cases in 2019.