Two countries in Africa have now been declared free of the Ebola virus. On Friday, the World Health Organization announced that Senegal had completely contained the spread of the disease, and now on Monday Nigeria has joined them.

The ruling was made after officials determined that Nigeria has gone six weeks without any new cases of the disease. The last reported case was on September 5. Seven Nigerians have died of the disease since July, but the country is being praised for swift and decisive efforts to contain the outbreak. In particular, Nigerian officials quickly traced all those who came into contact with the first person to be diagnosed with the disease this summer and kept them under strict observation and quarantine.

However, the problem is far from over in the three nations hardest hit by the outbreak—Liberia, Sierra Leone, and Guinea. About 4,500 people have died and the situation is nowhere close to being under control.

Meanwhile, in the United States, nearly all of those being monitored after coming in contact with Thomas Duncan, the first diagnosed patient in Texas, have reached the end of the 21-day monitoring period, after which they can be cleared free of the disease, if they haven't shown any symptoms.