As health officials try pinpoint the "breach of protocol" that caused Texas nurse Nina Pham to become infected with the Ebola virus, some are questioning whether the U.S. is fully prepared to stop the spread of the deadly virus here. There's a lot of confusion about Ebola and how it is spread. Here's what you need to know:
How many cases of Ebola are in the U.S.?
There have been two confirmed cases of Ebola here — Thomas Eric Duncan, the Liberian man who died on Oct. 8 and Nina Pham, the 26-year-old who cared for him during his second visit to the hospital. Duncan was infected during a visit to Liberia.
Pham, who was identified Monday, is a critical care nurse at the Dallas hospital, trained to deal with “life-threatening problems," according to NBC News. She is the first known direct transmission in the U.S.
She was in stable condition Sunday at Texas Health Presbyterian Hospital Dallas.
After all the medical precautions, how did the Texas health care worker get infected?
Health care workers, even when wearing protective gear, are known to be at high risk of contracting the infection. The Dallas nurse wore personal protective equipment (PPE) when caring for Duncan —the Liberian Ebola victim who died on Oct. 8 —and was considered low risk.
She was not one of the original 48 people who were being watched for their exposure to Duncan.
Officials at the Centers of Disease Control and Prevention say an undetermined medical error is responsible for the Dallas nurse's infection. The investigation is focused on a problem with the precautions taken during two procedures that were used during Duncan's care — kidney dialysis and respiratory intubation (breathing tube).
"Both of these procedures may spread contamination materials and are considered his risk procedures," Dr. Thomas Frieden, director of the CDC, said Sunday.
Even when wearing protective gear, it's as important how you put it on and how you take it off.
"Removing the equipment can really be the highest risk. You have to be extremely careful and have somebody watching you to make sure you remember all the steps," said Dr. Eileen Farnon, a Temple University doctor who formerly worked at the CDC and led teams investigating past Ebola outbreaks in Africa.
"After every step you usually would do hand hygiene," washing your hands with antiseptic or being sprayed with a chlorine spray, she said.
What about other health care workers who came into contact with the Ebola patient?
Health officials will now monitor all the hospital workers who were caring for Duncan even with full protective gear, according to the CDC. The original group of 48 contacts of Duncan have a week to go on their 21-day monitoring period and are still being watched for signs of infection.
The CDC is also recommending that the number of health care workers that care for potential Ebola cases be kept to a minimum.
What is being done for the infected health care worker in Dallas?
Frieden said Sunday every possible care is being given to the nurse. They are also checking with anyone who may have come into contact with her after she developed symptoms. At the Dallas news conference, officials said one person who had close contact with the health worker has been put into isolation and that 18 other people who had lesser degree of contact were being monitored.
When is Ebola contagious?
Only when someone is showing symptoms, which can start with vague symptoms including a fever, flu-like body aches and abdominal pain, and then vomiting and diarrhea.
How does Ebola spread?
Ebola doesn't drift through the air like germs that cause measles or tuberculosis. It is spread through close contact with a symptomatic person's bodily fluids, such as blood, vomit, feces, urine, saliva or semen. Those fluids must have an entry point, like a cut or scrape or someone touching the nose, mouth or eyes with contaminated hands, or being splashed. That's why health care workers wear protective gloves and other equipment.
The World Health Organization says blood, feces and vomit are the most infectious fluids, while the virus is found in saliva mostly once patients are severely ill.
Doctors say that, as yet, there is no evidence anyone has ever been infected via sweat.
What about more casual contact?
Again, Ebola isn't airborne. Forty years of studying Ebola outbreaks show the danger comes from being close to sick people.
Frieden has said people don't get exposed by sitting next to someone on the bus.
"This is not like flu. It's not like measles, not like the common cold. It's not as spreadable, it's not as infectious as those conditions," said Frieden.
Who gets tested when an Ebola infection is suspected?
Hospitals with a suspected case call their health department or the CDC to go through a checklist to determine the person's level of risk. Among the questions are whether the person reports a risky contact with a known Ebola patient, how sick they are and whether an alternative diagnosis is more likely. Most initially suspicious cases in the U.S. haven't met the criteria for testing.
How is it cleaned up?
The virus doesn't live long outside the body. Bleach kills it and plain soap and water can wash it away. Dried virus on surfaces survives only for several hours.
The CDC has strict guidelines for the handling of Ebola victims' bodies, because the virus can be transmitted in postmortem care settings. Bodies infected with Ebola virus should be cremated, not embalmed, or buried in a hermetically sealed casket.
Can dogs spread it?
No one knows. No case of Ebola spreading between dogs and people has ever been documented. But at least one study suggests dogs may be able to get Ebola without showing symptoms.On Monday, Dallas officials confirmed to NBC News that Bentley, the Cavalier King Charles Spaniel belonging to Ebola patient nurse Nina Pham, will be held in isolation for 21 days at a yet-to-be-determined facility.
Authorities euthanized the pet dog of the Spanish nursing assistant who caught Ebola while caring for a patient there.
This story was originally published October 11. It has been updated to reflect developments in Ebola cases in the U.S.
--NBC News senior health writer Maggie Fox, The Associated Press and health editor Jane Weaver contributed to this report