The US Centers for Disease Control and Prevention (CDC) on Monday issued tightened guidelines for healthcare workers caring for patients with Ebola.

Under the new guidelines, which came after two Texas nurses contracted the deadly virus while caring for a patient from Liberia, no skin should be exposed when personal protective equipment (PPE) is worn, given "the intensive and invasive care" that US hospitals provide for Ebola patients.

The CDC said healthcare workers must choose between two sets of PPE, currently used by the Emory University Hospital and Nebraska Medical Center, where four Ebola patients brought back from West Africa have been successfully treated.

The agency also recommended healthcare workers use double gloves, boot covers that are waterproof and go to at least mid-calf or leg covers, single-use fluid resistant gown that extends to at least mid-calf or coverall without intergraded hood, disposable full-face shield and surgical hoods that completely cover the head and neck.

The gear should also include respirators, either N95 respirators or powered air purifying respirator.

In addition, apron that is waterproof and covers the torso to the level of the mid-calf should be used if Ebola patients have vomiting or diarrhea, said the CDC.

Goggles are no longer recommended, the agency noted, saying they may not provide complete skin coverage in comparison to a single use disposable full face shield.

The CDC also said all healthcare workers should receive rigorous and repeated training in putting on and taking off PPE before dealing with Ebola patients.

"Training is a critical aspect of ensuring infection control...CDC and partners will ramp up training offerings for healthcare personnel across the country," the agency said in a statement.

Meanwhile, all workers must be supervised by a trained monitor while taking on or off the equipment.

"This is to ensure each worker follows the step by step processes, especially to disinfect visibly contaminated PPE. The trained monitor can spot any missteps in real-time and immediately address it," CDC added.

So far, three Ebola patients have been diagnosed on US soil, including a Liberian national, Thomas Eric Duncan, who died in Texas on Oct. 8, and two nurses who were infected while caring for Duncan. US health officials said a "breach in protocol" apparently led to the nurses' infection, but they have not yet known what went wrong.