The World Health Organization has declared Nigeria Ebola-free, after 42 days of no new reported cases. Since the outbreak began, Nigeria has reported 20 people with Ebola, eight of them died. (Reuters)

The World Health Organization has declared Nigeria Ebola-free — after more than six weeks without a new case of the disease that has claimed the lives of more than 4,500 people in West Africa, mainly in Liberia, Sierra Leone and Guinea.

“Nigeria is now free of Ebola,” WHO representative Rui Gama Vaz told a news conference in the capital Abuja, Reuters reported. “This is a spectacular success story … It shows that Ebola can be contained but we must be clear that we have only won a battle. The war will only end when West Africa is also declared free of Ebola.”

The last reported case in Nigeria was confirmed Sept. 8. The nation’s response to Ebola is being held out as an example to the still-stricken West African nations, as well to Texas. 

Ebola hit Nigeria in July when an American-Liberian citizen, Patrick Sawyer, was diagnosed in Lagos with the disease — and Nigerian officials quickly declared a public health emergency. Sawyer later died.

It was a nightmare scenario with the potential to spiral out of control, given the bustling city of Lagos, Africa’s largest, is a major transportation hub.

In total, Nigeria reported 20 people with Ebola, according to WHO. Eight of them died. But John Vertefeuille, with the U.S. Centers for Disease Control and Prevention, said Nigeria took the right steps to stop it.

“Nigeria acted quickly and early and on a large scale” Vertefeuille told Agence France-Presse. “They acted aggressively, especially in terms of contact-tracing.”

Last week, WHO announced Senegal was free of the disease. The infection was brought to Senegal in August by a man who had traveled by road from Guinea to Dakar. The government of Senegal identified more than 70 people who had come in contact with the man and began testing anyone considered at high risk. On Sept. 5, the man tested negative, recovered and later returned to Guinea, according to a statement from WHO.

According to WHO, the success of Nigeria — Africa’s most populous nation — was attributable to ample funding, quick action and assistance from the WHO, the U.S. Centers for Disease Control and the non-profit Doctors Without Borders.

Here's how the virus spreads and how contact tracing works to stop outbreaks. (Gillian Brockell/The Washington Post)

Unlike the situation in Guinea, Liberia and Sierra Leone, “all identified contacts were physically monitored on a daily basis for 21 days. The few contacts who attempted to escape the monitoring system were all diligently tracked” by special teams and returned to observation.

The organization noted Nigeria had resources unavailable to the poorer nations of West Africa, including experienced epidemiologists and a virology lab associated with a teaching hospital at Lagos University.

Officials conducted house-to-house information campaigns, explaining the risks and the preventive measures necessary to keep control of the situation.