A Transportation Security Administration (TSA) agent waits for passengers in Miami, Florida, on 4 October 2011 Passengers from Liberia, Sierra Leone and Guinea will face added layers of security upon arrival in the US

Travellers from Ebola-affected countries will face increased security scrutiny at American airports.

The Department of Homeland Security has ordered agents at airports and other ports to "observe" arrivals for potential signs of Ebola infection.

Passengers from Liberia, Sierra Leone and Guinea will have their temperatures taken and have to answer questions, according to CNN.

The deadly Ebola outbreak has already infected more than 7,200 people.

The new security measures, rolled out by the Transportation Security Administration, will reportedly take effect this weekend or early next week.

Homeland Security's deputy secretary, Alejandro Mayorkas, told reporters on Wednesday that Customs and Border Protection agents would be on the lookout for "general signs of illness" at US points of entry.

Factsheets will also be distributed to travellers with information on symptoms of Ebola and instructions to call a doctor if they become ill within three weeks.

US President Barack Obama speaks with members of his national security team and senior staff about the Ebola outbreak in West Africa,Barack Obama criticised foreign governments for not stepping up their response to the West Africa outbreak

On Monday, US President Obama announced the upcoming plans, saying "we don't have a lot of margin of error" in containing the spread of the deadly virus.

More than 3,400 people have already died in West Africa, and Liberian national Thomas Eric Duncan is in critical condition in Dallas after becoming the first person to be diagnosed with the disease outside Africa.

The first case of contagion outside that continent was also confirmed in Spain on Monday, where a nurse who treated an Ebola victim in Madrid contracted the virus herself.

Mr Obama, who spoke after a White House briefing with US health officials, said the US government would push to ensure doctors and other medical professionals responded appropriately if they came in contact with a patient with Ebola-like symptoms.

"We're also going to be working on protocols to do additional passenger screening both at the source and here in the United States," he said.

The US president also criticised foreign governments for not acting "as aggressively as they need to" against the outbreak.

"Countries that think that they can sit on the sidelines and just let the United States do it, that will result in a less effective response, a less speedy response, and that means that people die.

Thomas Duncan, shown at a 2011 wedding in GhanaMr Duncan, shown here at a 2011 wedding in Ghana

"And it also means that the potential spread of the disease beyond these areas in West Africa becomes more imminent," Mr Obama said.

Passengers leaving affected countries already have their temperatures checked, but people do not become infectious until they display symptoms.

Mr Duncan was screened for symptoms when he left Liberia but appeared healthy. He did not develop symptoms of Ebola until four days later, when he was in the US.

Ten people who came into direct contact with him are being closely monitored but none has yet displayed any Ebola symptoms.

Dr Tom Frieden, director of the Centers for Disease Control and Prevention, has ruled out banning flights to the US, arguing the isolation would only worsen the outbreak within Africa and would deny those countries crucial aid.