Scientists across the United States say they cannot obtain samples of Ebola, complicating efforts to understand how the virus is mutating and develop new drugs, vaccines and diagnostics.

The problems reflect growing caution by regulators and transport companies about handling Ebola as well as the limited resources of West African countries which are struggling to help thousands of infected citizens.

Ten scientists from eight major research institutions contacted by Reuters reported they were unable to get Ebola samples in recent months.

No one really knows right now what the virus has mutated to or if it has mutated

Tulane University, one of the institutions, received samples this week, and the US Centres for Disease Control and Prevention said it has reached an agreement to get live specimens, but it is not clear if new supplies will satisfy demand, and transport remains challenging.

Ebola mutates as it spreads, and while few expect it to acquire the ability to transmit through air, for instance, scientists require a constant supply of fresh samples to track these changes. The samples hold up is not likely to delay the development of experimental treatments. But if the virus undergoes significant changes that go undetected, the drugs and tests might not work, researchers said.

Microbiologist and infectious disease expert Dr Charles Chiu of the University of California, San Francisco, needs samples from Ebola patients to develop a new genetic test that could detect the disease in infected individuals before symptoms appear.

“No one really knows right now what has the virus mutated to or if it has mutated,” he said. Without that research, “we’re not going to be able to determine in advance whether or not it has changed to a form where it might evade diagnostic assays or might render current vaccines or drugs ineffective.” Scientists say Liberia, Guinea and Sierra Leone have been slow to release samples as they fight to contain the worst Ebola outbreak on record which has killed about 5,000 people.

Laurie Garrett, the senior fellow for global health at the Council on Foreign Relations in New York, said the issue is largely about safe transport.

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