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Ebola Transmission: Health Care Worker Practice Most Important Consideration

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Not long after we learned that a health care worker treating Thomas Duncan has tested positive for Ebola, I ran across this terse tweet from Mackey Dunn, the pen name of Don Weiss, who is “a medical epidemiologist with the New York City Department of Health and Mental Hygiene”. The tweet linked to this short but incredibly important blog post. In the post, Weiss notes the baffling development that a health care worker, who wore full personal protective equipment (PPE), contracted Ebola from Duncan even though at this point, none of his family or other close contacts, who did not have full PPE, have developed symptoms of the disease.

That set of facts prompts Weiss to pose the question “So, what does this tell us about Ebola and how we can attain control?” His answer begins:

One, that Ebola patients become more infectious as the illness progresses. The newly reported case in a healthcare worker had onset on October 10th. If we take 9 days as the mean incubation period for Ebola this means the healthcare worker’s exposure was sometime around October 1, which was day 8 of Mr. Duncan’s illness. This is similar to what was seen with SARS, that patients become more infectious (and dangerous) with time.

In setting up the circumstances for his question, Weiss had noted that Duncan was hospitalized, ending exposure to family members, on day 5 of his disease.

Although he doesn’t mention it, this aspect of Ebola, where patients produce more virus and become more infectious during the course of a fatal infection, also accounts for why burial practices are so important to containing the spread of Ebola. Patients produce the most virus and are thus at their most infectious at death.

The converse also appears to be true. Duncan was symptom-free when he flew from Liberia to Dallas on September 19 to 20. At 24 days since the end of that trip, we have now passed the incubation period, commonly given as 2-21 days, for Ebola to develop in anyone who could have been exposed during the flights. No infections among those airline passengers have been reported. I have yet to see a major media outlet mention this point, though.

We are now at 16 days since Duncan was hospitalized, ending his family’s direct exposure, so we have passed the two-thirds point of the incubation period for them (and well past the 9 days that Weiss gives as the average incubation period for Ebola).

The second part of Weiss’ musings on the infection of the nurse is extremely important:

Second, that only hospitals that are well prepared to care for highly infectious patients should be allowed to do so. Standard practice is to have a staff person dedicated to observing the donning (putting on) and doffing (taking off) of PPE. This observation should continue throughout the period of clinical care (from an ante-room with a window). Perhaps gentle reminders during the doffing can avoid the presumed situation in Spain where the nurse may have touched her face with a gloved hand.

When a patient presents to a hospital early in the illness there is time to transfer to such a facility. That’s the plan here in NYC. Bellevue hospital has a specially equipped ward to care for Ebola patients. Their staff are well trained. The number of healthcare workers entering the room should be kept to a minimum, especially after day 7 of the illness.

Weiss was prescient in his push for an observer for workers putting on and taking off PPE. In today’s New York Times, we have this on the CDC’s thoughts regarding improving practices for health care workers treating Ebola patients: Read more →

CDC Director: “Zero Risk” to Passengers on Flights With Dallas Ebola Patient

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Although not yet widespread, panic and disinformation are emerging surrounding the case of the first patient to have been diagnosed with Ebola while in the United States. The worst of the hysteria surrounds the fact that Thomas E. Duncan flew from Liberia to the United States on a trip that required 28 hours, ending at the Dallas-Fort Worth airport on September 20. It is known that Duncan was screened in Liberia and found not to have a fever when he boarded the first flight. Persons infected with Ebola but not yet exhibiting symptoms are incapable of spreading the disease, primarily because the disease spreads through direct contact of mucous membranes or open wounds with bodily fluids and symptom-free patients are not yet vomiting or having diarrhea, so no virus-carrying fluids are being produced or at risk of being spread in ways that other people will come into contact with them.

On Tuesday, the Director of the CDC, Dr. Tom Frieden, stated outright that there is zero risk to passengers who were on a flight with Duncan:

A national public health official today said there was “zero risk of transmission” of Ebola on a commercial airline flight that a Dallas patient who has tested positive for the disease flew on from Liberia earlier this month.

Centers for Disease Control and Prevention Director Tom Frieden said today in a live briefing from Atlanta that the person — a male who remained unnamed — showed no symptoms before boarding the plane and was not contagious. The CDC doesn’t “believe there is any risk to anyone who was on the flight at that time,” he said.

Despite Frieden’s clear statement that other passengers face no risk, the press continued to hound CDC and the airlines until Duncan’s itinerary was released. While CBS was moderately responsible in their coverage of the flight information, the Daily Mail asked breathlessly in their headline whether YOU were on a flight with Duncan. Even more incredibly, stocks in US airlines were dumped yesterday in response to the news of Duncan’s flights:

Investors were also selling stocks following news that the first case of Ebola had been diagnosed in the U.S. Investors dumped airline stocks and bought a handful of drug companies working on experimental Ebola treatments.

The story of just how Duncan became infected is a sad one. On September 15 (recall that he left Liberia on the 19th and arrived in Dallas the 20th), Duncan helped neighbors take their 19-year-old daughter to the hospital. Sadly, the hospital was already overwhelmed with patients and she was turned away, only to die early the next morning after returning:

In a pattern often seen here in Monrovia, the Liberian capital, the family of the woman, Marthalene Williams, 19, took her by taxi to a hospital with Mr. Duncan’s help on Sept. 15 after failing to get an ambulance, said her parents, Emmanuel and Amie Williams. She was convulsing and seven months pregnant, they said.

Turned away from a hospital for lack of space in its Ebola treatment ward, the family said it took Ms. Williams back home in the evening, and that she died hours later, around 3 a.m.

Mr. Duncan, who was a family friend and also a tenant in a house owned by the Williams family, rode in the taxi in the front passenger seat while Ms. Williams, her father and her brother, Sonny Boy, shared the back seat, her parents said. Mr. Duncan then helped carry Ms. Williams, who was no longer able to walk, back to the family home that evening, neighbors said.

The hospital in Dallas where Duncan is being treated has received a lot of criticism because he first went there on September 26 but was sent home when only exhibiting a low grade fever:

When Mr. Duncan first arrived at the hospital last Friday, six days after he had arrived in America, he told a nurse that he had come from West Africa. Public health officials have been urging doctors and nurses to be on the alert for Ebola in anyone who has been in Guinea, Liberia or Sierra Leone. But information about Mr. Duncan’s travel was not “fully communicated” to the full medical team, said Dr. Mark Lester, executive vice president of Texas Health Resources, the parent organization that oversees Texas Health Presbyterian Hospital.

As a result, that information was not used in the clinical diagnosis and Mr. Duncan was sent home, with the diagnostic team believing he simply had a low-grade fever from a viral infection, Dr. Lester said.

Those with whom Duncan had contact from the time of the onset of his symptoms until he returned the hospital on September 30 28 (corrected; September 30 was when tests confirmed Ebola after he returned to the hospital on September 28) in much worse condition and was then isolated are being monitored for signs that they may be infected:

Officials said Wednesday that they believed Mr. Duncan came into contact with 12 to 18 people when he was experiencing active symptoms and when the disease was contagious, and that the daily monitoring of those people had not yet shown them to be infected.

The incubation period (the time between exposure to the disease and the onset of symptoms in an infected person) for Ebola varies from 2 to 21 days. Recall that Duncan was exposed on September 15 and visited the hospital for the first time on September 26, so his incubation period was around eleven days. We are now around six days into the time since Duncan first visited the hospital, so those with whom he came into contact will need to be monitored for for another two weeks or so until at least 21 days have passed since their last contact with Duncan.

While there is some chance that one or more of those with whom Duncan had contact while he was contagious will become infected, as long as everyone who was in contact with him during that critical period is under observation now, there is virtually no chance of the disease spreading outside that small group of people. And you can rest assured that nobody from any of the flights Duncan was on will come down with disease from exposure to him.