Atlanta (CNN) -- A Nigerian doctor has been diagnosed with Ebola nearly three weeks after a Liberian-American man with Ebola died after traveling to Lagos, Nigerian officials said Monday. Nigerian Minister of Health Onyebuchi Chukwu told reporters that the infected physician had been treating Patrick Sawyer, a top government official in the Liberian Ministry of Finance who died of Ebola in a Nigerian hospital July 20. Eight other people are being quarantined and three are awaiting Ebola test results, the health minister said. Read more about Patrick Sawyer's death .
Diagnosis comes three weeks after Liberian-American man died from virus . "We know what needs to be done," CDC director says . Experts will also help implement stronger systems to fight the disease, CDC chief says .