France's prime minister tested positive for COVID-19 on Monday, hours after returning from a visit to neighboring Belgium and just as France is seeing a nationwide resurgence of infections, according to his office.

The positive test also means that his Belgian counterpart Alexander De Croo and four other minister immediately went into quarantine since they met with Castex for talks in Brussels earlier Monday.

French Prime Minister Jean Castex will adapt his schedule for the coming 10 days to continue his activities in isolation, his office said. Officials at the prime minister's headquarters did not comment on whether Castex has any virus symptoms.

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One of Castex's daughters tested positive Monday after her father returned from a meeting with Belgian Prime Minister Alexander de Croo in Brussels, and Castex himself then took two tests that were both positive, his office said.

De Croo's office said he will be tested Wednesday and will self-isolate while awaiting the result, as will the foreign affairs, defense, justice and home ministers.

“Since Prime Minister De Croo received the French Prime Minister for security talks, he has immediately interrupted his activities,” a statement from his office said.

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While 75% of France's population is vaccinated, the number of virus infections has risen quickly in recent weeks. Hospitalizations and deaths linked to the virus are also rising in France, though are so far well below the crisis levels of earlier surges.

French President Emmanuel Macron contracted COVID-19 last December, and other government ministers have also had the virus.