Apple (AAPL -0.60%) announced on Friday that all 42 of its retail stores in China had reopened, after some were shuttered for nearly a month, the result of the outbreak of COVID-19 illness caused by the SARS-CoV-2 coronavirus.

The retail stores are a key component of Apple's strategy in China, and the company warned last month that it would likely not meet its revenue guidance for the March quarter. The company cited two contributing factors: temporary iPhone supply constraints brought on by production facilities that were ramping up more slowly than Apple had anticipated and closures of both its retail and partner stores in the country. 

Apple Store Qingdao China

The Apple Store in Qingdao, China. Image source: Apple.

iPhone sales in China plunged in February, selling just 500,000 units and falling by nearly 60% year over year, according to government data. 

It appears the supply pinch may be easing as well, as Foxconn -- one of Apple's main iPhone assemblers -- said the number of employees returning to work "exceeded our expectations and imagination" and that parts supplies were returning to normal levels. The company said it expects to return to full production by month's end.

Having these retail stores open for business is big news for Apple, who has been dealt a debilitating setback in its recovery efforts. Last year, the tech giant was reeling from the slowing economy in China and the trade war between Washington, D.C. and Beijing, which resulted in four consecutive quarters of year-over-year revenue declines. Apple appeared to have turned the corner last quarter when it reported all-time record revenue that increased by 9%. The outbreak resulted in a setback to the company's recovery, however, as it makes 15% of its sales in China.

Apple's troubles may not be over, however, as it recently decided to close all its retail stores in Italy to help contain the outbreak there.