Ighalo recently moved to England from China, where the Coronavirus epidemic, which has claimed over 700 lives and spread to more than 20 countries, originated.
United Kingdom immigration officials have been directed to tighten restrictions on people who have been to China in the past fortnight and United fear the 30-year-old former Nigerian international might not be allowed back into the country.
Ighalo, who took a pay cut to join the Red Devils on a six-month contract, will instead follow a personal training programme in Manchester while his new teammates jet off to Spain.
United manager Ole Gunnar Solskjaer told MUTV: "Odion will stay in Manchester, because since he has come from China in the last 14 days, the news of the virus there [means] we're not sure if he's going to be allowed back into England if he leaves the country again.
"So he's staying here working with a personal coach on an individual programme and his family then can settle in England as well. That's a plus.
"Of course he might have liked to have come with the players and got to know them, but we don't want to take that risk [of potential border restrictions tightening]."
Manchester United will return to England on Friday ahead of their Premier League game with Chelsea three days later.
