President Barack Obama on Saturday urged Americans not to succumb to hysteria about Ebola, even as he warned that addressing the deadly virus would require citizens, government leaders and the media to all pitch in.

As he did so, a Texas-based cruise ship was reported to be returning to port in Galveston after a woman onboard isolated herself, fearing she could have Ebola.

The woman onboard the Carnival Magic is employed in laboratories at the Dallas hospital which treated Thomas Eric Duncan, the first man to die of Ebola in the US, who was treated by two nurses who have contracted the disease. The government of Belize reportedly refused to airlift the woman back to the US.

In a statement, Carnival Cruise Lines, citing “an extreme abundance of caution”, said: “The Texas healthcare worker onboard continues to show no symptoms of illness and poses no risk to guests and crew onboard.”

On Friday, the secretary of state, John Kerry, used a speech at the state department to say Ebola could become “a scourge like HIV or polio, that we will end up fighting, all of us, for decades”. The president of Liberia, one of the three west African countries most affected by the outbreak, reportedly telephoned the mayor of Dallas to apologise for the arrival of the disease in his city via one of her citizens.

On Saturday, the charity Oxfam warned that more must be done to prevent Ebola becoming “the disaster of our time”, while the World Health Organisation promised it would publish a full review of its handling of the Ebola crisis once the outbreak was under control, in response to a leaked document that appeared to acknowledge it had failed to do enough.

The WHO said in a statement that it would not comment on an internal document cited in an Associated Press story on Friday, saying it was a first draft that had not been fact-checked and was “part of an on-going analysis of our response”.

“We cannot divert our limited resources from the urgent response to do a detailed analysis of the past response. That review will come, but only after this outbreak is over,” the organisation said.

Fidel Castro, meanwhile, said Cuba was ready to cooperate with the US in the battle against Ebola. The 88-year-old ex-leader wrote in state news media on Saturday that cooperation would be in the interest of “the peace of the world”.

Cuba has sent 165 doctors and nurses to help fight Ebola in Sierra Leone and plans to send 296 others soon to Liberia and Guinea. That effort has brought unusual praise from Kerry.

The Canadian government said it would ship 800 vials of its experimental Ebola vaccine to the WHO in Geneva, beginning on Monday.

Facebook Twitter Pinterest Tourists enjoy a ride on a catamaran as cruise ship Carnival Magic is seen near the shores of Cozumel on Friday. Photograph: Reuters

In his weekly address, Obama also pushed back against calls for the US to institute a travel ban. Lawmakers have called it a commonsense step to prevent more people with Ebola from entering the US, but Obama said such a ban would only hamper aid efforts and screening measures.

“Trying to seal off an entire region of the world – if that were even possible – could actually make the situation worse,” the president said.

Growing US concern about Ebola and the three cases diagnosed so far in Dallas prompted Obama on Friday to tap a former top White House adviser to be his point person on Ebola. Striking a careful balance, Obama said there was no “outbreak” or “epidemic” of Ebola in the US, but said even one case was too many.

“This is a serious disease, but we can’t give in to hysteria or fear – because that only makes it harder to get people the accurate information they need,” Obama said. “We have to be guided by the science.”

As Obama sought to reassure anxious Americans, US officials were still working to contain the fallout from the Ebola cases identified in the US so far, rushing to cut off potential routes of infection for those who may have come into contact with individuals who contracted Ebola.

Obama said he was “absolutely confident” the US could prevent a serious outbreak at home – if it continues to elevate facts over fear.

“Fighting this disease will take time,” Obama said. “Before this is over, we may see more isolated cases here in America. But we know how to wage this fight.”