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Epidemiological modelling based on the data from previous EBOV outbreaks has produced a basic reproduction number (R0) of 2.7 with a 95% confidence range of 1.9 to 4.1 (Legrand et al., 2007). This R0 is comparable to influenza (Mills et al., 2004) and would seem to be comfortably within the range required to generate an EVD pandemic. In answer to the question of why this has not already occurred in human history, perhaps the most persuasive response is that EVD very fortunately only emerged into human populations around the time of its discovery in the mid-1970s (Walsh et al., 2005), by which time we were fairly equipped to deal with it in remote low population density settings. Whether we can contain it within a large city, should the necessity to do so arise, remains to be seen.
originally posted by: netwarrior
a reply to: TinkerHaus
Respectfully, you are incorrect about a virus never changing modes of transmission. Ebola Reston went airborne in 1989. By sheer chance, that same mutation caused it to be asymptomatic in humans.
Pigs seem to give off more aerosolized viral particles than other species, says Derek Gatherer, a viral evolutionary biologist at Lancaster University in England. “If it’s going to spread by aerosols, then pigs are the species to do it,” he says.
But he doesn’t think the researchers definitively demonstrated airborne transmission of the Ebola virus. Virus-laden droplets of water could have splashed from the pig pen to the macaque cages when the researchers washed the pig enclosure, he says.
Pigs probably aren’t a source of Ebola outbreaks. Few have even been found to carry Ebola. Pigs in the Philippines have been found to carry Reston ebolavirus, a species of Ebola that does not cause disease in people. No African pigs are known to be infected with Zaire ebolavirus, the cause of the current epidemic.
Even if pigs can transmit the virus by air, they may be unique in the ability. The new study, published July 25 in Scientific Reports by Kobinger and a different group of collaborators, found no evidence that sick macaques could give the virus to healthy monkeys through airborne particles.
Fabian Leendertz, an epidemiologist and disease ecologist at the Robert Koch Institute in Berlin, says that the outbreak is spreading by human-to-human contact. The people who are dying are mostly women who care for the sick, their children and people who touch dead bodies during funeral rituals, he says. Health care workers are also at risk.
But Ebola is not nearly as easily transmitted as many people assume, he says. Even if an infected person were to hop on a plane and fly to the United States, Europe, or elsewhere, Leendertz says, tight health care measures would ensure that Ebola “will never get far.”
I understand your point, but I still must point to the fact that we've never once witnessed a virus changing it's transmission method. At the link I provided earlier, the virologist states that multiple amino acids need to change for this to happen - and we've yet to witness it happening naturally.
To date, the idea of a virus "going airborne" is not a reality. At least not in nature.
Molecular Epidemiology and Brief History of Emerging Adenovirus 14—Associated Respiratory Disease in the United States
Background. First isolated in the Netherlands in 1955 during an outbreak of acute respiratory disease (ARD) among military recruits, human adenovirus 14 (HAdV-14) has historically been considered rare.With no precedent of circulation in North America, HAdV-14 has been isolated from military and civilian cases of ARD of variable severity since 2003 in the United States.
Methods. Ninety-nine isolates from military and civilian cases from different geographic locations and circulation periods were characterized by restriction enzyme analysis of viral DNA and select gene sequencing.
Results. All examined viruses were found to be identical and to belong to a new genome type designated “HAdV-14p1” (formerly known as “14a”). Comparative alignments of E1A, hexon, and fiber gene sequences with other subspecies B2 HAdVs suggest that HAdV-14p1, like the closely related HAdV-11a, arose from recombination among similar HAdV-11 and HAdV-14 ancestral strains. A deletion of 2 amino acids in the knob region of the fiber protein is the only identified unique characteristic of HAdV-14p1.
Conclusion. The current geographic distribution of HAdV-14p1 involves at least 15 states in the Unites States. The role of the fiber mutations in the recent emergence of HAdV-14p1 ARD in North America warrants further study.
Human adenoviruses (HAdVs) include 52 recognized serotypes assigned to 7 species (A–G) on the basis of biophysical, biochemical, and genetic criteria . Species B includes 2 genetic clusters, subspecies B1 and B2. The serotypes of subspecies B1 (HAdV-3, HAdV-7, HAdV-16, HAdV-21, and HAdV-50) generally cause acute respiratory disease (ARD), whereas the serotypes of subspecies B2 (HAdV-11, HAdV-14, HAdV-34, and HAdV-35) are more often associated with urinary tract infections and opportunistic infections of immunocompromised hosts .
As an example, consider a unique ecological challenge faced by many pathogens: appropriate habitats can be few and alarmingly far between. Put yourself in the position of a virus in its natural habitat — a human host. You've infected some cells and managed to reproduce, but the host's immune system is onto you now and is turning up the heat. This environment is no longer so hospitable. How can you get your descendents to a friendlier habitat (i.e., a new, unexploited human body)? Without legs, wings, fins, or any of the usual means of locomotion, your descendents' prospects for reaching a new host under their own power are nil. However, natural selection has provided pathogens with a number of sneaky strategies for making the leap to a new host, including:
Droplet transmission — for example, being passed along when one host accidentally sneezes on another. The flu is transmitted this way.
Airborne transmission — for example, being exhaled by one host and inhaled by another. Tuberculosis is transmitted this way.
Vector transmission — getting picked up by a carrier (the vector — e.g., a mosquito) and carried to a new host. Malaria is transmitted this way.
Waterborne transmission — leaving one host (e.g., in feces), infecting the water supply, and being taken up (e.g., in drinking water) by a new host. Cholera is transmitted this way.
Sit-and-wait transmission — being able to live outside a host for long periods of time until coming into contact with a new host. Smallpox can survive for years outside of a host!
Pathogen lineages that fail to meet this challenge and never infect a new host are doomed. They will go extinct when their human host dies or when the immune system destroys the infection.
Do you think we might be facing the beginnings of a pandemic?
There will certainly be Ebola patients from Africa who come to us in the hopes of receiving treatment. And they might even infect a few people here who may then die. But an outbreak in Europe or North America would quickly be brought under control. I am more worried about the many people from India who work in trade or industry in west Africa. It would only take one of them to become infected, travel to India to visit relatives during the virus's incubation period, and then, once he becomes sick, go to a public hospital there. Doctors and nurses in India, too, often don't wear protective gloves. They would immediately become infected and spread the virus.
The virus is continually changing its genetic makeup. The more people who become infected, the greater the chance becomes that it will mutate ...
... which might speed its spread. Yes, that really is the apocalyptic scenario. Humans are actually just an accidental host for the virus, and not a good one. From the perspective of a virus, it isn't desirable for its host, within which the pathogen hopes to multiply, to die so quickly. It would be much better for the virus to allow us to stay alive longer.
Could the virus suddenly change itself such that it could be spread through the air?
Like measles, you mean? Luckily that is extremely unlikely. But a mutation that would allow Ebola patients to live a couple of weeks longer is certainly possible and would be advantageous for the virus. But that would allow Ebola patients to infect many, many more people than is currently the case.
But that is just speculation, isn't it?
Certainly. But it is just one of many possible ways the virus could change to spread itself more easily. And it is clear that the virus is mutating.
So, says Dr. Levine, "The media's claim is not totally without scientific basis. But there are no precedents for it, and it's unlikely.
"I think it's irresponsible to raise that concern," she added, "because in general viruses are very well-adapted to their milieuand they don't just suddenly change their environment." Will this kind of level-headed assessment quell media hysteria? Stay tuned.
When news broke that the Ebola virus had resurfaced in Uganda, investigators in Canada were making headlines of their own with research indicating the deadly virus may spread between species, through the air.
The team, comprised of researchers from the National Centre for Foreign Animal Disease, the University of Manitoba, and the Public Health Agency of Canada, observed transmission of Ebola from pigs to monkeys. They first inoculated a number of piglets with the Zaire strain of the Ebola virus. Ebola-Zaire is the deadliest strain, with mortality rates up to 90 percent. The piglets were then placed in a room with four cynomolgus macaques, a species of monkey commonly used in laboratories. The animals were separated by wire cages to prevent direct contact between the species.
Within a few days, the inoculated piglets showed clinical signs of infection indicative of Ebola infection. In pigs, Ebola generally causes respiratory illness and increased temperature. Nine days after infection, all piglets appeared to have recovered from the disease.
Within eight days of exposure, two of the four monkeys showed signs of Ebola infection. Four days later, the remaining two monkeys were sick too. It is possible that the first two monkeys infected the other two, but transmission between non-human primates has never before been observed in a lab setting.
While the study provided evidence that transmission of Ebola between species is possible, researchers still cannot say for certain how that transmission actually occurred. There are three likely candidates for the route of transmission: airborne, droplet, or fomites.
- See more at: healthmap.org...
In fact, there’s almost no historical precedent for any virus to change its basic mode of transmission so radically.
originally posted by: cuckooold
a reply to: boncho
I'm not downplaying it, but rather addressing the question, is there too much fear mongering? I've read threads from people saying we should ban vey flight from Africa, while others believe it's some form of global population control from the illuminati, shadow government, or some other hidden entity.
originally posted by: ZiggyMojo
I think the rate at which Ebola infects is dependent so far on geography and the population density.
A Spanish nurse has become the first person to be infected with Ebola outside of West Africa after contracting the virus while treating a missionary who died in a Madrid hospital, Spain’s health ministry said Monday.
Ana Mato, Spain’s health minister, told a televised news conference that the nurse tested positive for Ebola twice, and that the rest of the 30-person team that looked after the missionary were undergoing medical tests to determine whether they had contracted Ebola.
When it comes to viruses, it is always difficult to predict what they can or cannot do. It is instructive, however, to see what viruses have done in the past, and use that information to guide our thinking. Therefore we can ask: has any human virus ever changed its mode of transmission?
The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted.