The centre-back is nearly ready to rejoin Spurs' training sessions but will not be available to face former club Southampton, while Lloris is struggling due to illness.
"I don't know [if Lloris will be fit]," Pochettino told reporters on Friday. "Difficult to say.
"We need to wait today and tomorrow and then assess him tomorrow and if he's available or not. I think it's a flu or a virus. It's between this.
"I think everyone, with this weather, apart from today's fantastic weather, has struggled a little bit. It's an epidemic across Europe, not just here in the UK."
While Michel Vorm may have to deputise for the France goalkeeper on Sunday, long-term absentee Alderweireld is closing in on a return to first-team action.
"Maybe today if all is OK with him then tomorrow he can integrate himself in some exercise with the group and a little bit step by step build his fitness to be available again," Pochettino said. "Tomorrow, but if all is OK with a scan today.
"I am very pleased when the players that are injured are in their preparation to return like Harry Winks or in this case, Toby or Danny Rose. I think every manager wants all their players fit and available to select.
"That is the most important thing. We have a very busy period ahead and we need all the team fit and available to play."
Tottenham traditionally do not do much business in the mid-season transfer window, with Lewis Holtby and DeAndre Yedlin two of the only January arrivals in recent years.
And Pochettino is not expecting things to change in 2018, although his side are three points adrift of Champions League qualification ahead of the Argentinian's return to St Mary's.
"To be honest, it's difficult but in some point you always dream," said Pochettino, who denied reports Chelsea have made a bid for striker Fernando Llorente. "But not too much exciting. If it happens, it happens, if not happen, then not happen. We're happy with the squad.
"I am not a specialist in the market. I think I am a specialist in football and sometimes not too much. The market is the market and it's difficult to assess. For the specialists, it is difficult to predict what is happening and what is going on.
"People that think one year or ago or six months ago something wouldn't happen and now it is happening. The most important thing is to be happy with everything that is moving around you. But I am not a specialist in the market and I cannot tell what is going on."