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Biology is rarely black or white, all or nothing. Protective immunity is generally not an on/off switch, where from the moment you're vaccinated you're infinitely resistant for the rest of your life. You shouldn't expect that, having received a smallpox vaccine, you could have billions of smallpox viruses squirted directly into your lungs and shrug it off ...


79

Do they exist? Yes What are they called? Marilyn Roossinck calls them viral mutualistic symbiotes. She has an excellent review here. What are some examples? My personal favorite is GB-Virus C, or Hepatitis G, which appears to slow the progression of HIV using a number of different mechanisms: Box 1. Summary of the effects of GBV-C infection in HIV-...


76

Since 2000, in the United States alone, there were 16 reports of outbreaks or groups of outbreaks where the outbreak started with an initial case in an unvaccinated individual and resulted in disease in previously vaccinated individuals. The epidemiology of pertussis is a little different, and transmission happens in many cases apart from a clear outbreak, ...


54

It doesn't. Viruses don't "know" anything. Mutations occur at random. Most of them don't do anything, or have a slight negative effect on the ability of the virus to infect and reproduce. However, there are billions and billions of viruses. Once in a while a random mutation will offer a significant advantage like immunity to an anti-viral drug. The viruses ...


50

Short answer: There is no benefit for their use in households. Long answer: These soaps (see here for the complete list) contain the so called quaternary ammonium compounds Benzalkonium chloride and Cetrimonium chloride which indeed have antimicrobial properties. While they do not promote resistance to these compounds (see reference 1), their use is still ...


36

The bacteria wouldn't see any benefit from the warm water in the ~30-60 seconds you're washing your hands, neither would hot water "sterilize" your hands at temperatures you could tolerate. The reason you wash your hands with hot water is because the hot water+detergent soap mix is better for removing oil and dirt than cold water+detergent, which is ...


36

Do physicians/biologists not know all the different types of viruses out there? No, Biologists don't know all the viruses that exist out there. There's a lot! We do know many of the ones infecting humans, though, especially the ones leading to the most common diseases. The fact that the doctor didn't know what type of virus she has bothers me. ...


36

When differences between prokaryotes and eukaryotes are taught in an introductory biology course, a generic prokaryotic cell and a generic eukaryotic cell are typically compared. Cells in a complex multicellular organism, like a human, are quite diverse. Human red blood cells are one example of a highly specialized cell with a mature form that is quite ...


32

Mainly cost/benefit analysis. Using vaccines has a cost, both in dollars and in risk. That cost may be very low (cheap safe vaccines, like measles vaccine), or may be relatively high (smallpox vaccine is relatively risky, with around a 1 in 300,000 chance of moderate to severe side effects); but there is always some cost. Vaccines may not have any ...


28

An autoclave can sterilize both solids and liquids, whereas an oven with no pressure control is typically not suitable to sterilize liquids. Not only do you need to heat the chamber to 121°C, but you also need to make sure that the things you are trying to sterilize are not degraded by the treatment. For dry objects (e.g. glassware) you could heat the ...


25

First, and I cannot stress this enough, you should not go seeking out human pathogens if you don't have the appropriate equipment to handle it at the right safety level. That goes for all pathogens, even ones you might find around your house. In a professional lab, you might get samples from collaborators, clinical samples, vendor, or really an number of ...


25

Another good virus would be a Bacteriophage, a virus that infects and kills illness-causing bacteria. From Wiki: A bacteriophage also known informally as a phage, is a virus that infects and replicates within Bacteria and Archaea. The term was derived from "bacteria" and the Greek φαγεῖν (phagein), "to devour". Bacteriophages are ...


25

How long should I wait before handling the parcel to avoid contracting the virus? If you use gloves, or don't touch your face and just wash your hands after opening, you don't have to wait at all. If you don't use gloves or want to pick your nose, rub your eyes, or fiddle with your beard while opening the package, wait 24 hours if the package is nonporous, ...


24

It's a cost/benefit situation. Yes they could have taken samples, processed them, teased out the virus, and eventually identified exactly what virus (sort of*) that your girlfriend had by its gene sequence. But do you want to pay 10k-100k per virus to find that out, or just pay $20-100 and take some fluids and be fine. I say sort of because viruses tend ...


19

What is a microbe? A microbe (or microorganism) is a microscopic organism. Anything that is considered alive and that is small enough is called a microbe. Note that this definition has two issues. There is no universally accepted definition of life. There is no universally accepted size threshold for being called a microbe (to my knowledge). I would go ...


19

From the UK National Health Service: Flu viruses capable of being transferred to hands and causing an infection can survive on hard surfaces for 24 hours. Infectious flu viruses can survive on tissues for only 15 minutes. Like cold viruses, infectious flu viruses survive for much shorter periods on the hands. After 5 minutes the amount of flu virus on hands ...


18

Do all bacterial cells have a double membrane? No. There are a number of bacterial membrane and cell wall structures. Some of them have a double membrane, some of them don't. In microbiology, we often make the initial distinction between two groups of bacteria based on whether or not they take up an iodine based stain called a Gram stain. Gram negative ...


18

I would say that if any "good" viruses exist, they are already within us. Retrotransposons are genetic elements in our DNA that were likely ancient viruses and they move around from time to time either by excising themselves and moving somewhere else or by making a copy and inserting it somewhere else in the genome. Even though we are born with them, their ...


17

70% ethanol is the minimum concentration when used in a lab setting for aseptic technique. You don't want to go lower, because it will not kill the microorganisms you are trying to kill. However the solution requires water to be effective at doing its job. The 30% water is necessary to provide sufficient polarity to the solution. EDIT A rough ...


17

The quick answer is: Yes, it can cause harm. Think about it...The septic system (both the tank and your "drain field") rely on bacteria, and antibacterial soap is not designed to kill only specific species of bacteria. In other words, antibacterial soap can kill a whole range of bacteria, and that certainly includes the bacteria needed in your ...


16

One of the most common toxins in mouldy food/bread is aflatoxin. The exposure to high amount of aflatoxin can lead to acute aflatoxicosis with fulminant hepatic failure and even death. While mild exposure to aflatoxin could be asymptomatic, it is better not to take a chance considering possible complications (citation from the link above): Aflatoxins ...


16

This is actually an interesting question! Let me answer both the parts separately, taking the example of Listerine® mouthwash. Is an antiseptic's inability to eliminate 100% of all germs due to its "chemistry", or is it due to physical factors? In most of the cases, this is due to the physical factors. Clearly, your mouth is not a flat surface. It has ...


16

We have engineered a few good viruses to treat certain diseases Per my comment and response: The most current example (at this time and based on my recollection) is the virus we have engineered to treat a certain type of macro degenerative eye condition: Scientists Have Reversed Age-Related Blindness by Deliberately Infecting Eyes With a Virus There are a ...


15

This is an embryonic stem cell on the tip of a needle photographed on a scanning electron microscope (SEM). The image was taken by Steve Gschmeissner, see here for the original.


15

Ventricaria ventricosa (previously called Valonia ventricosa) is not exactly a single cell. It has a coenocytic structure with multiple nuclei and chloroplasts. As Jasand Pruski correctly guessed the organism possesses a large central vacuole which is multilobular in structure (lobules radiating from a central spheroid region). The entire cell contains ...


14

Reasons for Bacteria with different shapes as given in Wikipedia/Bacteria: The wide variety of shapes is determined by the bacterial cell wall and cytoskeleton, and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators. There is an article based on research by ...


14

Chris has correctly identified the antibacterial agent in the hand soap depicted in the image in the question, and therefore his answer is superior as a direct answer. Nevertheless, other members of the Softsoap series of hand soap uses triclosan, 0.15% as their antibacterial agent, as seen in an image of their ingredient list on the reverse of the bottle. ...


14

Cowpox and smallpox viruses structurally similar, and catching one confers immunity to both by immune system response, but one was a deadly disease and the other almost harmless. Once this was discovered, the days of smallpox were numbered. We had the means and the motivation to stamp it out. On my last check a few years ago, we are deliberately keeping ...


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