Quarantines ordered by some US states for doctors and nurses returning from West African countries hit by Ebola have a "chilling effect" on aid work in those countries, aid group Doctors Without Borders (MSF) has said.



MSF told the Reuters news agency on Friday that the restrictions imposed by several states on returning doctors, were forcing some of their workers to delay their return to the US, to avoid facing stigmatisation and possible quarantine.



"There is rising anxiety and confusion among MSF staff members in the field over what they may face when they return home upon completion of their assignments in West Africa," Sophie Delaunay, executive director of MSF in the United States said.





"Some people are being discouraged by their families from returning to the field," Delaunay said.



The governors of New York and New Jersey announced strict new screening rules at airports last Friday, including mandatory 21-day quarantines for people who have had contact with Ebola patients in West Africa



MSF's comments come after Craig Spencer, a doctor returning from West Africa, was hospitalised in New York City last week with the virus.



Then, last Friday, Kaci Hickox, a nurse who worked for MSF in Sierra Leone, was confined to a tent against her will for several days after arriving at Newark Liberty International Airport in New Jersey. Hickox, who tested negative for Ebola and says she is completely healthy, has mounted a personal protest against the quarantine policy.



'Not grounded in science'



MSF said they were discussing whether to shorten some Ebola assignments from their current duration of four to six weeks. Aid workers typically begin and end their assignments in Brussels, the Belgian capital, a spokesman said.



Last weekend, US President Barack Obama's administration criticised the quarantining of healthy people as "not grounded in science," echoing criticisms from public health experts.



Delaunay's comments on Thursday are the most substantive criticism of the rules since they were announced, suggesting they are reducing MSF's manpower and forcing American workers into temporary exile in Europe.



MSF says the policies have also created a misconception that healthcare workers are endangering the public, even though a person who does not have symptoms cannot spread the virus.



The aid group had already made a policy of asking its workers not to return to their regular jobs for 21 days after finishing an Ebola assignment. It pays them wages for that time.



Delaunay, the MSF director, also said there were fears among its workers that other countries may follow the example set by some US states.



About 5,000 people have died from Ebola over the past six months, particularly in Liberia, Guinea and Sierra Leone.