Human viruses harm

Don't said:. Meh said:. Comment on rabies fatality rate. Although all warm-blooded animals are thought to be susceptible to rabies, there are strains of the rabies virus multiple bat stains strains are maintained in particular reservoir host s , with some cross over especially in the US between raccoons and skunks.

Although a strain can cause rabies in other species, the virus usually dies out during serial passage in species to which it is not adapted, and non-carnivores cows, horses, deer, groundhogs, beavers AND CATS, like small rodents, are dead-end hosts. The CDC estimates in the US, 1 million dollars per potential life saved is spent by post-exposure prophylaxis in cases of exposure to animals other than bats, canines, fox, raccoon, skunks.

Hundreds of unvaccinated cats are infected with, and die or are euthanized of rabies each year -no way every human exposure to "the kitten in the park " is tracked down. Certainly, many farmers and ranchers are unknowingly exposed. Yet almost all of the people diagnosed in the US yearly, knew they were bitten by a dog when outside the US or handled a bat. And there have been several incidences since , where people got rabies secondary to solid organ transplants.

Species vary in susceptibility to various strains, humans are 'most' susceptible to canine rabies and, in the US, the silver-haired bat strain. This is a solitary bat with infrequent human interaction, whereas we have much more exposure to big and little brown bats and Mexican free-tailed bats.

Only a small percentage of any of these have rabies, -it kills them too! The virus needs to get to a nerve, so if a bite is not deep enough, or a small viral load is deposited, or the 'victim' immune system responds - an infection will never be established.

If the virus is able to get to a nerve, it attempts to travel up an axon, to the brain- again, the immune system may eliminate. As rabies is a slow virus, it can self -immunize, explaining the presence of rabies neutralizing antibodies in Amazonian Indians and others who have never been vaccinated? The reason why a mature dog is considered immunized 28 days after its first rabies vaccination, is if it has been exposed or is 'incubating' rabies virus but the virus is more than 28 days away the vaccine will prevent infection.

Although antiglobulin is given, PEP - a killed vaccine, is basically, rapid immunization. Since definitive diagnosis is made on brain biopsy, the apparent spontaneous cures or response to treatment remain unproven. Not to diminish the threat or the misery of this disease. I don't understand why the WHO estimate of deaths has been quoted as 35, to 55, for the last 40 years - while the world population went from approximately 4 billion to 8 billion, mostly in Africa and Asia where few dogs are vaccinated and most cases are seen.

Jim Thompson MD said:. Viruses also provide a variety of services for plants. A few plants grow in the hot soils surrounding the geysers and the "Artists' Paintpots" of Yellowstone National Park.

One such plant, which is a type of tropical panic grass, is a symbiosis that includes a fungus that colonizes the plant, and a virus that infects that fungus. All three members of this symbiosis are necessary for survival in soils simmering at more than degrees Fahrenheit. In the laboratory, Roossinck has created symbioses between the same virus-infected fungus and other plants. This has enabled every plant her group has tested to survive at these elevated soil temperatures, including tomato, she says, noting that she has pushed the soil temperature to degrees without killing the plant.

Investigators have also found that certain viruses can render some plants drought tolerant, and at least one example of virally-conferred cold tolerance has been discovered-- discoveries that could become useful for expanding the ranges of crops. Plants are often infected with "persistent viruses" that are passed down from generation to generation, perhaps over thousands of years, with viruses that are transmitted to nearly percent of their plant progeny, but that have never been shown to be transmitted from one plant to another.

Other beneficial viruses are the ancient retroviruses that long ago made a permanent home in the genome, or that left genes therein, said Roossinck. I was always a little disturbed at the bad rap they get, so it was very exciting for me to find good ones. This mirrors what we observe for bacteria as well. Many of the viruses living inside us do not target our cells. Instead they look for the bacteria in our microbiomes. Known as bacteriophages , or phages, these viruses sneak inside bacterial cells, use the machinery there to make copies of themselves, then often burst out to infect more bacteria, killing their host cells in the process.

Bacteriophages are nearly ubiquitous in nature. If you look hard enough, you will find them in soil, in any source of water from the ocean to your tap at home, and in extreme environments such as acid mines, the Arctic and hot springs.

You will even find them floating in the air. They persist in all these places because they are hunting the bacteria that live in all these places. We humans are just another hunting ground. In Sophie Nguyen and Jeremy Barr, then at San Diego State University, demonstrated that many phages get to their final locations in the body by crossing through mucosal membranes.

In laboratory experiments, phages worked through membranes that line the intestine, lung, liver, kidney, even the brain.

But when they randomly cross into a place such as the central nervous system, where there are few bacteria to be hosts, they may have no way to replicate and may ultimately perish. The virome can vary greatly from one part of the body to another. When Ghose and I looked for viruses in unexpected places, we also determined that viruses in the mouth are different from viruses in the gut, which are different from viruses in urine or in blood.

We knew this was the case for bacteria, but early on we did not have enough data for viruses. Although it is not hard to find volunteers who will spit in a cup, it is hard to get them to provide stool or blood samples and to persuade universities to sign off on obtaining and processing these samples.

When we do have the goods, we must filter out the bacteria, leaving tiny bits of viral material we can examine under a microscope and insert into a machine that sequences the nucleic acids that encode the genes that are present. Still, researchers have done enough of this work now to be able to tell what part of the body they are examining just by noting the viruses present. My colleague Melissa Ly of the University of California, San Diego, and I have also shown that by comparing the viromes of unrelated people we can determine if any of them live together.

Although different people can have significantly different viromes, people who cohabitate appear to share about 25 percent of the viruses in their viromes.

Viruses can be transmitted from one household member to the other not just through typical contagious means such as coughing but also through casual contact and sharing sinks, toilets, desks and food.

Although we have only studied small numbers of people, the data show that nonromantic roommates share a similar percentage of viruses as romantic roommates do. Intimate contact seems to make little difference; just living in the same space is enough. The puzzle is tricky, however. Shira Abeles, also at U. San Diego, has identified big differences in the oral viromes of men and women; hormones could be the reason, but no one has demonstrated such a connection.

We do know that viromes can vary considerably with geographic populations. For example, there is less diversity in the viromes of individuals in Western countries than there is among individuals in non-Western countries. These differences may be related to both diet and environment. Many viruses in our virome infect bacteria, but a smaller proportion infect cells in our tissues directly.

These viruses may be in the minority because our immune system suppresses them. Iwijn De Vlaminck, then at Stanford University, demonstrated that when a person's immune system is strongly challenged—for example, when someone has received an organ transplant and must take immunosuppressing drugs to avoid rejecting the organ—the presence of certain viruses increases dramatically.

In these cases, we see a rise in both viruses known to cause disease and those that do not. This observation suggests that under normal circumstances our immune system keeps the virome in check, but when immunity is hampered, viruses can multiply readily. The most common are a secondary bacterial pneumonia, or bacteremia a rise of bacteria in the bloodstream , involving organisms such as Staphylococcus aureus and Streptococcus pneumoniae.

Though less common, we have also seen viral coinfections such as influenza, respiratory syncytial virus and adenovirus. Viruses lurking in the virome may also reactivate, such as Epstein-Barr virus and cytomegalovirus. When the immune system is paying attention to COVID, the patient may be more susceptible to other viral outbreaks. Many phages, despite being hunters, live in harmony with their prey for a long time and may never break out.

Viruses are mostly known for their aggressive and infectious nature. It's true, most viruses have a pathogenic relationship with their hosts — meaning they cause diseases ranging from a mild cold to serious conditions like severe acute respiratory syndrome SARS.

They work by invading the host cell , taking over its cellular machinery and releasing new viral particles that go on to infect more cells and cause illness. But they're not all bad.

Some viruses can actually kill bacteria, while others can fight against more dangerous viruses. So like protective bacteria probiotics , we have several protective viruses in our body. Bacteriophages or "phages" are viruses that infect and destroy specific bacteria.

They're found in the mucus membrane lining in the digestive, respiratory and reproductive tracts. Mucus is a thick, jelly-like material that provides a physical barrier against invading bacteria and protects the underlying cells from being infected.