Nedohin managed a 7-5 win over Russia's Anna Sidorova on Tuesday without regular second Jessica Mair.
"She did have a bit of a rough night, but was feeling better by this morning," Nedohin said. "Stomach flu, I hope. She's getting medical assistance this morning."
Canada was tied for first with Ji-Sun Kim of South Korea at 5-1. Nedohin had a game at night against Sweden's Margaretha Sigfriddson (4-2).
Illness is a theme running through championship curling events in Canada this year. A vicious stomach bug knocked several players out of multiple games at the Canadian women's championship last month in Red Deer, Alta., although Nedohin's team dodged it.
Ontario lead Craig Savill sat out two games early at the Canadian men's championship with similar symptoms, but played on the final weekend for Glenn Howard who won the Brier.
Mair took herself out of the previous night's loss to Denmark after the sixth end. Alternate Amy Nixon came off the bench cold and curled 98 per cent, but the Canadians lost that game in an extra end.
Nixon was back in the lineup against Russia and was rated at 78 per cent.
"I play better going in cold. So if I play again, I'll wait until the very last second," Nixon said wryly. "I'm hoping Jessica can come back because it's a lot easier with your core team members, but I'm ready to go if necessary."
Curling teams routinely book a hotel room that can serve as a quarantine room. Nixon has moved in with lead Laine Peters so Mair can have her own quarters.
Dealing with illness on the team is easier when the world championship is in Canada because of familiarity with the medical system, Nedohin said. But it's also stressful for a player to take herself out of the game.
"It's really crummy as a player," Nedohin said. "You could see it in her eyes last night. She was crying. We all want to be here. It's hard not to have Jess, but it's not a big deal.
"It's Tuesday and we'll have her back by the playoffs."
The top four teams advance to playoffs at the conclusion of the round robin Thursday.
South Korea's Kim, the surprise of this world championship, stole single points in the 10th and an extra end to beat Denmark's Lene Nielson 9-8 in the afternoon draw.
Kim won just two games at last year's world championship in Esjberg, Denmark. The petite skip's hands were shaking after pulling out the win.
"Very fun, or . . . unbelievable," she said. "I very, very (much) wanted to win."
Canada faces the South Koreans on Wednesday morning.
"I think it will be very difficult," Kim said. "That's OK, no problem. Not scared. (We're) ready."
Sweden and Switzerland's Mirjam Ott was 4-2 ahead of Russia, Denmark, Scotland's Eve Muirhead and Germany's Melanie Robillard at 3-4.
Linda Klimova of the Czech Republic, China's Bingyu Wang, Allison Pottinger of the U.S., and Diana Gaspari of Italy were all 2-4.
The success of Nedohin's team is partly due to their on-ice chemistry. Nedohin and vice Beth Iskiw banter at the back of the house, while lead Peters and Mair often break into giggles while they're sweeping.
A lineup change has the potential to be disruptive, but Peters and Nixon, the two Calgary-based players on the team, play in a league together.
"We're buddies," Nixon said. "We play on a Wednesday-night league team. We were out there today and I said 'It's exactly like league.'"
Russia seems not to care about team chemistry. It's a common practice by coach Olga Andrianova to move players in and out of the lineup based on their performance.
Third Liudmila Privivkova was benched the previous day, but was inserted into the game after the fourth end against Canada at second for Nkeiruka Ezekh.
The Russians spend considerable time in North America playing World Curling Tour events in order to prepare their team for the 2014 Winter Olympics in Sochi, Russia. Their game is familiar to Nedohin, if the makeup of their team isn't.
"I recognized everyone of them. The only uncertainty is what their lineup is going to be," she said. "It's ever-changing."
Nixon brings the experience of playing in an Olympic Games. She was third for Shannon Kleibrink's team that won bronze in 2006 in Turin, Italy.
She knows what it's like to be sick at a major championship. Nixon had a similar bug while playing in the semifinal and bronze-medal games at the Olympics.
"I can exactly imagine how Jess feels. It's so stressful and frustrating and heart-wrenching," Nixon said. "You want to come in when you can, but you're not exactly sure how you're going to feel when you get sweeping. It's a hard call to make."
Nixon recently parted company with Kleibrink after nine years to skip her own team. Kleibrink's not the only elite women's team to make changes. Amber Holland, last year's Canadian champion, said earlier this week she's disbanding her Kronau, Sask., foursome.
"What Amber Holland said yesterday kind of resonated with me, which is every team has its time,'' Nixon said.
"We had a good run. It's a great team with great players. I think they'll be wildly successful without me. I thought it was time to do something different."