Measures have been introduced in two African states aimed at stopping the spread of the new coronavirus, joining countries worldwide who have imposed restrictions since the disease surfaced in central China last month.No verified infection has been reported to date in sub-Saharan Africa, but elsewhere countries have stopped flights to China and airlifted their citizens out of the area where the virus emerged. Equatorial Guinea on Tuesday quarantined four travellers who arrived from Beijing, the government said.The four had arrived aboard an Ethiopian Airlines flight at the airport in the capital of Malabo, the government of the small central African state said in a statement on Wednesday.On Monday, the prime minister's office had announced that all passengers from China would be placed in quarantine for 14 days, "corresponding to the incubation period of the disease."China has also asked its nationals who have recently arrived or returned to the West African state of Mauritania to remain confined for at least 14 days to prevent the possible spread of the virus, the Chinese embassy in Nouakchott said.There was no indication that the message was motivated by any specific situation in Mauritania. The embassy also advised Chinese planning to travel to Mauritania to postpone their trip. It said those already in the country should communicate daily about their health and avoid public gatherings.Experts say the potential spread of the virus in Africa is a concern because of the poor healthcare infrastructure in many parts of the continent.An oil-rich state with an entrenched record of authoritarian rule and poverty, Equatorial Guinea has developed close economic ties with Beijing.Chinese companies have been awarded a string of contracts for infrastructure projects.The Mauritanian government has set up a crisis unit and placed thermal cameras at the airports of Nouakchott and Nouadhibou.Many of the Chinese in Mauritania work in technical assistance, Chinese projects and trade operations, but there no direct flights between the two countries.