A series of missteps at the nation’s top public health agency caused a critical shortage of reliable laboratory tests for the coronavirus, hobbling the federal response as the pandemic spread across the country like wildfire. In the critical month of February, as the virus began taking root in the U.S. population, CDC data shows government labs processed 352 COVID-19 tests — an average of only a dozen per day, an Associated Press review found. Outside observers and federal health officials have pointed to four primary issues that together hampered the national response — the early decision not to use the test adopted by the World Health Organization, flaws with the more complex test developed by the CDC, government guidelines restricting who could be tested and delays in engaging the private sector to ramp up testing capacity.