DALLAS - The United States issued stringent new protocols on Monday for health workers treating Ebola victims, directing medical teams to wear protective gear that leaves no skin or hair exposed when caring for patients infected with the virus.

The new guidelines from the US Centers for Disease Control and Prevention in Atlanta come as 43 people who were exposed to the first patient diagnosed in the United States were declared risk free, easing a national sense of crisis over the spread of Ebola.

Under the CDC protocols, Ebola healthcare workers must undergo special training and demonstrate competency in using protective equipment designed to prevent their exposure. Use of the gear, now including coveralls, and single-use, disposable hoods, must be overseen by a supervisor to ensure proper procedures are followed.

A key element is that no skin can be exposed by doctors, nurses or technicians taking care of a person infected with Ebola, which is transmitted through direct contact with bodily fluids and tissue but is not airborne.

The hemorrhagic fever has killed more than 4,500 people in the West African nations of Liberia, Sierra Leone and Guinea.

"Even a single healthcare worker infection is unacceptable," CDC Director Tom Frieden said in a teleconference with reporters outlining the new regulations.

There have been just three cases of Ebola diagnosed inside the United States, a Liberian man, Thomas Eric Duncan, who died in Dallas, Texas, on Oct 8, and two nurses who treated him and are now themselves patients.

Among those declared risk free on Monday were four people who shared an apartment with Duncan and had been in quarantine.

The old guidelines for health workers, based on World Health Organization protocols, said they should wear masks or goggles but allowed some skin exposure.