Did you know most of infectious diseases in human are originated from animals. Historically, human blames domestic animal that cause the disease, but wild animal also the major culprit transmitted the disease in human including HIV. HIV or AIDS is believed originated from chimpanzees.
How the disease transmitted from animal to human? The process by which a pathogen of animals evolves into one exclusive to humans occurs in five stages. Agents can become stuck in any of these stages. Those in early stages may be very deadly (Ebola, for example), but they claim few lives overall because they cannot spread freely among humans. The better able a virus is to propagate in humans, the more likely it is to become a pandemic. The 5 stages:
Stage 1: Pathogen is present in animals but has not been detected in humans under natural conditions.
Stage 2: Animal pathogen has been transmitted to humans but not between humans.
Stage 3: Animal pathogen that can be transmitted between humans causes an outbreak of disease but only for a short period before dying out.
Stage 4: Pathogen exists in animals and undergoes a regular cycle of animal-to-human transmission but also sustains long outbreaks arising from human-to-human transmission.
Stage 5: Pathogen has become exclusive to humans
It can be illustrate by the figure below:
The people in the rural area or native people is more chance to in contact with wild animal ( more possibility the disease to transfer) because everyday in their daily life, they make contact with wild type animal- as food, or pets.
How we prevent it? Nathan Wolfe is Lorry I. Lokey Visiting Professor in Human Biology at Stanford University and the director of the Global Viral Forecasting Initiative has take one prevention method to curb the emergence of pandemic. Their initiated a study of viruses in rural villagers in the Central African country of Cameroon who hunt and butcher wild animals, as well as keep them as pets. They were trying to determine whether new strains of HIV were entering into human populations, and They suspected that these people would be at particularly high risk of infection. By taking their blood samples, their analyses of the blood from the hunters and the hunted revealed several animal viruses not previously seen in humans. One agent, which they first reported in a paper published in 2004 in Lancet, is known as simian foamy virus (SFV), and it is a member of the same family of viruses— the so-called retroviruses—to which HIV belongs. SFV is native to most primates, including guenon monkeys, mandrills and gorillas, and each of these primate species harbors its own genetically distinctive variant of the bug. We found that all three variants had entered the hunter populations. In one particularly telling example, a 45-year-old man who reported having hunted and butchered gorillas—animals rarely pursued by subsistence hunters—had contracted gorilla SFV.
In those same Central African populations they also found a variety of retroviruses known as human T lymphotropic viruses (HTLVs), so named because of their propensity for infecting immune cells called T lymphocytes. Two of the HTLVs, HTLV-1 and HTLV-2, were already well known to affect millions of people around the world and contribute to cancer and neurological disease in some infected individuals. But HTLV-3 and HTLV-4, which we described in 2005 in the Proceedings of the National Academy of Sciences USA, were new to science. Given the high degree of genetic similarity between HTLV-3 and its simian counterpart, STLV-3, it appears as if this virus was picked up through hunting STLV-3-infected monkeys. The origin of HTLV-4 remains unclear, but perhaps they will find its primate ancestor as they continue to explore these viruses in monkeys. They do not yet know whether SFV or the new HTLVs cause illness in people. Viruses do not necessarily make their hosts sick, and viruses that do sicken people and even spread from person to person do not always cause pandemics; often they retreat spontaneously. But the fact that SFV and HTLV are in the same family as HIV, which did spawn a global epidemic, means that epidemiologists must keep a close eye on them.
By using that method, (epidemiology study) on the rural area, the emergence of new types of virus can be detect and the further action can be taken to prevent it to be pandemic. WHO has taken this action to all possible place in this world to detect the emergence of viruses in particular types of disease. For example, In Malaysia, the viruses tha previously spawned is Nipah virus and the target population is wildlife hunters.
Had we been watching hunters 30 years ago, we might have been able to catch HIV early, before i t reached the pandemic state. But that moment has passed. The question now is, How can we prevent the next big killers? Once they (Nathan Wolfe and colleague) had determined that we could study remote populations effectively, we knew we could extend our work more broadly to listen in on viral “chatter”—the pattern of transfer of animal viruses to humans. With global surveillance, we realized, we might be able to sound the alarm about an emerging infectious disease before it boils over.
Main reference- from article in Scientific American Magazines April 2009 titled "Preventing The next Pandemic"
No comments:
Post a Comment