(Bloomberg) -- China’s Covid-19 cases jumped to almost 700 as Shanghai widened a testing blitz to cover around 20 million of the city’s residents. 

The country reported 699 cases for Monday -- the highest since May 22 -- after recording more than 1,000 cases over the weekend. 

The spike in cases underscores the difficulty of achieving the country’s Covid Zero strategy in the face of more infectious strains of the virus. President Xi Jinping has made Covid Zero a hallmark of his rule, saying the country won’t pursue “herd immunity” like other countries because it would exact too much of a toll, particularly on China’s elderly, which have low vaccination rates.

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The latest hotspots include the Guangxi autonomous region in the south of China, which recorded 243 cases on Monday, taking its total since the outbreak flared six days ago to 829. The northwestern province of Gansu reported 231 infections for Monday, taking the number of cases found in the past week to 953. 

In Shanghai, which is rolling out a testing blitz this week in 12 of the city’s 16 districts, cases rose to 23 on Monday from 17 on Sunday. All the new cases were found in areas already under quarantine. The districts account for about 80% of the financial hub’s 25 million residents. 

The capital, Beijing, reported one case for Monday, CCTV reported, breaking a seven-day streak of zero cases. 

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