Newcastle head coach Steve Bruce fears two of his players are suffering from long-term Covid-19.
Bruce has revealed two unnamed members of his squad will not be available for Saturday's Premier League clash with Fulham after testing positive for coronavirus, and could be missing for several more weeks.
He said: 'You accept injuries, but a virus like this is obviously new to everybody. I've seen the effect now it has on extremely fit, young professional footballers and the effect it's had on them, and two of them in particular.
'Yes, we're at a disadvantage and we hope, for my sake as well as the players', they do recover properly and give them time to recover because it's the welfare of them and their long-term health.
'This long-term Covid, if one or two of them have got it like they seem to have, then it's very, very difficult to manage.'
Midfielder Isaac Hayden had played in the last two games and defender Federico Fernandez returned against Leeds in midweek having recovered from the virus after an outbreak forced the closure of the club's training ground and the postponement of their trip to Aston Villa earlier this month.
The Magpies have not named those affected, but Javier Manquillo, Jamaal Lascelles, Fabian Schar and Allan Saint-Maximin are among those players who have been unavailable for recent games.
Bruce said: 'We have still got four or five of the squad missing through illness, so it's been a difficult time in that respect.
'However, we are seeing a light at the end of the tunnel that we hope we can get them all back. Certainly we have got one or two, though, who are finding it a struggle at the moment.
'My concern now is for their well-being and their welfare because now they've been struggling for a while with it.'