Expertos del CIEI temen que el ébola pueda transmitirse por vía respiratoria

Nota del doctor Michael Osterholm, para Blog de Juan Prado

Hoy en día, el virus del Ébola solo se propaga a través del contacto directo con fluidos corporales, como la sangre y el vómito. Pero a algunos de los principales expertos en enfermedades infecciosas en Estados Unidos les preocupa que este virus mortal pueda mutar y transmitirse sólo a través de la tos o un estornudo.

"Es la principal preocupación que he tenido en mis 40 años de carrera en la salud pública", dijo el doctor Michael Osterholm, director del Centro de Investigación de Enfermedades Infecciosas de la Universidad de Minnesota.

"No me puedo imaginar nada en mi carrera – y esto incluye el VIH – que pudiera ser más devastador para el mundo que un virus del Ébola transmisible por vía respiratoria".

Osterholm y otros expertos dicen que son relativamente pequeñas las posibilidades de que el virus del Ébola haga la transición para que pueda transmitirse por la tos o por un estornudo.

Cada vez que otra persona se infecta de ébola, el virus tiene otra oportunidad de mutar y desarrollar nuevas capacidades. Osterholm lo llama "ruleta genética".

Hasta este viernes, se han registrado 4.784 casos de ébola, con 2.400 muertes, según la Organización Mundial de la Salud, que dice que el virus se está propagando a un ritmo mucho más rápido de lo que ocurría al principio del brote.

El ébola es un virus ARN, lo que significa que, cada vez que se copia, tiene una o dos mutaciones.

Muchas de esas mutaciones no significan nada, pero algunas de ellas podrían ser capaces de cambiar la forma en que el virus se comporta en el interior del cuerpo humano.

"Imaginen que cada vez que se copia un ensayo, se cambian una o dos palabras. Finalmente, se va a cambiar el significado del ensayo", dijo el médico CJ Peters, uno de los héroes que aparecen en The Hot Zone.

Ese libro narra el brote de Ébola Reston, que se transmitió entre monos por vía respiratoria en 1989. En 2012, investigadores canadienses hallaron que el Ébola Zaire, que está implicado en el brote actual, se transmite de los cerdos a los monos en el aire.

James Le Duc, director del Laboratorio Nacional de Galveston de la Universidad de Texas, dice que el problema del Ébola es que nadie hace el seguimiento de las mutaciones que ocurren en África occidental, por lo que nadie sabe realmente en qué se ha convertido el virus.

Un grupo de investigadores analizó cómo el Ébola cambió en un corto periodo de tiempo en una sola ciudad en Sierra Leona, desde el inicio del brote, antes de que se propagara tan rápido como ahora. Encontraron más de 300 cambios genéticos en el virus.

"Es aterrador ver lo mucho que ha mutado este virus en solo tres semanas", dijo el médico Pardis Sabeti, profesor asociado en la Universidad de Harvard y miembro asociado senior del Instituto Broad, donde se realizó la investigación.

Incluso sin la mutación, se ha requerido un gran esfuerzo para detener el virus.

Médicos Sin Fronteras dice que Monrovia, Liberia, necesita 1.000 camas para pacientes de ébola, pero sólo tiene 240, y se ha tenido que rechazar a pacientes, enviándolos de nuevo a barrios en los que es probable que infecten a más personas.

In English

Today, the Ebola virus spreads only through direct contact with bodily fluids, such as blood and vomit. But some of the nation's top infectious disease experts worry that this deadly virus could mutate and be transmitted just by a cough or a sneeze.

"It's the single greatest concern I've ever had in my 40-year public health career," said Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. "I can't imagine anything in my career -- and this includes HIV -- that would be more devastating to the world than a respiratory transmissible Ebola virus."

Osterholm and other experts couldn't think of another virus that has made the transition from non-airborne to airborne in humans. They say the chances are relatively small that Ebola will make that jump. But as the virus spreads, they warned, the likelihood increases.

Every time a new person gets Ebola, the virus gets another chance to mutate and develop new capabilities. Osterholm calls it "genetic roulette."

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As of Friday, there have been 4,784 cases of Ebola, with 2,400 deaths, according to the World Health Organization, which says the virus is spreading at a much faster rate now than it was earlier in the outbreak.

Ebola is an RNA virus, which means every time it copies itself, it makes one or two mutations. Many of those mutations mean nothing, but some of them might be able to change the way the virus behaves inside the human body.

"Imagine every time you copy an essay, you change a word or two. Eventually, it's going to change the meaning of the essay," said Dr. C.J. Peters, one of the heroes featured in "The Hot Zone."

That book chronicles the 1989 outbreak of Ebola Reston, which was transmitted among monkeys by breathing. In 2012, Canadian researchers found that Ebola Zaire, which is involved in the current outbreak, was passed from pigs to monkeys in the air.

Dr. James Le Duc, the director of the Galveston National Laboratory at the University of Texas, said the problem is that no one is keeping track of the mutations happening across West Africa, so no one really knows what the virus has become.

One group of researchers looked at how Ebola changed over a short period of time in just one area in Sierra Leone early on in the outbreak, before it was spreading as fast as it is now. They found more than 300 genetic changes in the virus.

"It's frightening to look at how much this virus mutated within just three weeks," said Dr. Pardis Sabeti, an associate professor at Harvard and senior associate member of the Broad Institute, where the research was done.

Even without becoming airborne, the virus has overwhelmed efforts to stop it.

The group Doctors Without Borders says Monrovia, Liberia, needs 1,000 beds for Ebola patients but has only 240, and it has had to turn patients away, sending them back to neighborhoods where they could infect more people.

This week, a Pentagon spokesman said the United States is sending a 25-bed field hospital to Monrovia.

"A 25-bed hospital with nobody to staff it? That's not the scale we need to be thinking about," Le Duc said. "It's an absolute embarrassment. When there was a typhoon in the Philippines, the Navy was there in 48 hours and had billions of dollars in resources."

Osterholm commended groups like Doctors Without Borders but said uncoordinated efforts by individual organizations are no match for Ebola spreading swiftly through urban areas.

"This is largely dysfunctional. Nobody's in command, and nobody's in charge," he said. "It's like not having air traffic control at an airport. The planes would just crash into each other."