Liberia was declared free of the Ebola virus by global health experts on 14 January, a milestone that signalled an end to an epidemic in West Africa that has killed more than 11,300 people. But the World Health Organization (WHO) warned there could still be flare-ups of the disease in the region, which has suffered the worlds deadliest outbreak over the past two years, as survivors can carry the virus for many months and could pass it on.

Health specialists cautioned against complacency, saying the world was still underprepared for any future outbreaks of the disease.

Today WHO declares the end of the most recent outbreak of Ebola virus disease in Liberia, the outbreak that was associated with the flare-up of cases in mid-November, said Rick Brennan, Emergency Risk Management and Humanitarian Response for WHO. Its also the first time that all three countries in West Africa, Guinea, Sierra Leone and Liberia, have stopped all known chains of transmission of the disease since the outbreak started in 2014.

But the WHO official warned that: We have to say that the job is still not done. Thats because there is still ongoing risk of re-emergence of the disease, because of persistence of the virus in a proportion of survivors.

Liberia was the last affected country to get the all-clear, with no cases of Ebola for 42 days, twice the length of the viruss incubation period – the time elapsed between transmission of the disease and the appearance of symptoms. The other affected countries, Guinea and Sierra Leone, were declared Ebola-free late in 2015.

There were cases in seven other countries including Nigeria, the United States and Spain, but almost all the deaths were in the West African nations. It is the first time since the start of the EVD (Ebola Virus Disease) epidemic in West Africa almost two years ago that the three hardest-hit countries, Guinea, Liberia and Sierra Leone, are at zero cases for at least 42 days, said WHOs Liberia representative Alex Gasasira.