20-year-old Poromaa is one of four men who have been selected for the race, together with Calle Halfvarsson, Jens Burman and Björn Sandström.
On the women's side, Charlotte Kalla, Emma Ribom, Frida Karlsson and Ebba Andersson compete.
Both Kalla and Halfvarsson have been question marks ahead of the WC.
Kalla has struggled with back problems and was ill with corona last autumn, and Halfvarsson has struggled with form.
But both were part of the championship squad that was presented two weeks ago.
Johaug favorite
At the WC in Seefeld 2019, Frida Karlsson was the Swede who was closest to threatening Therese Johaug in the skiathlon.
Karlsson finished fifth and Charlotte Kalla sixth, both were over a minute behind Johaug.
Ebba Andersson missed that competition due to irritation in the airways.
The 23-year-old has shown good form during the season and won, among other things, the final stage up Alpe Cermis in the Tour de Ski and was on the podium in the World Cup in Falun a month ago.
Pointing out Ebba
Johaug also pointed out Andersson as his biggest competitor at a press conference on Friday.
- Ebba is the strongest.
She has shown very good form in recent races, said Johaug.
Sweden started the WC in Oberstdorf with a gold when Jonna Sundling won the women's sprint yesterday.
CLIP: Johaug's tribute to Charlotte Kalla: "A fantastic athlete"
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Therese Johaug's tribute to Charlotte Kalla: "A fantastic athlete"