9

They ran out of samples Their test is destructive, they can't test the same sample twice. They planned out a number of samples to test for each time period and tested them. At the end of six weeks, they were done. It doesn't really matter The point of the paper is that HCV is infectious long-term on surfaces when not cleaned properly, indicating there is ...


9

“Swine flu” is an obsolete name. The official name for the virus that was briefly called “swine flu” is “H1N1pdm09”. H1N1pdm09 has a mortality rate of around 0.01-0.1%. That’s roughly 10- to 20-fold lower than COVID-19. Its R0 was estimated at between 1 and 2, which is roughly half the estimates for SARS-CoV-2 (the virus responsible for COVID-19]. A ...


6

There are a number of currently used aerosolized vaccines throughout the world. Generally, these are studied and administered in single individual doses. There are advocates for the use of larger, sealed exposure chambers for rapid administration of vaccines to large numbers of people, possibly in the field, for example in a tent like this figure from the ...


6

It is plausible but by no means established that antipyretics (fever suppressors) in particular could increase the duration of infection/symptoms, because fever is part of a functional immune response. From Graham et al 1990 (a small [n=56] randomized trial of the use of antipyretic pain relievers in volunteers experimentally infected with rhinovirus): ...


6

I have reared cockroaches by the thousands, for years. Three species, but mainly the infamous Periplaneta americana which I am sure everyone has at least heard about (see picture at the end). First of all: Cockroaches do bite, and they have powerful mandibles. This is in the paper below: https://doi.org/10.1371/journal.pone.0141226 Many people think they ...


6

CDC Wonder, a health database of the US Center of Disease Control and Prevention (CDC), has weekly data for Nationally Notifiable Infectious Diseases and Conditions, United States: Weekly Tables from 1996 to 2020 on the state level for antrax, brucellosis, dengue fever, leptospirosis, malaria, meningococcal disease, Q fever, rabies, etc. Weekly tables since ...


6

Gastrointestinal infections can be caused by Gram positive and negative bacteria: Gram-positive: Staphylococcus aureus Clostridium difficile, botulinum and perfringens Listeria monocytogenes Bacillus cereus Gram-negative: Salmonella enteritidis and typhi Campylobacter jejuni Shigella Escherichia coli Vibrio cholerae and parahaemolyticus Helicobacter ...


6

According to Merriam-Webster Dictionary a Pandemic is: an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population : a pandemic outbreak of a disease Epidemics are considered a smaller scale version of a pandemic affecting a smaller region, community or population. Epidemics are obviously ...


5

The common cold as a clinical syndrome is not any particular viral infection, but a cluster of symptoms that follow a stereotypical course. It's generally associated with an initial viral infection and you can isolate infectious particles early in the course of the illness, but by the time most people go to the doctor there is no active infection. Because of ...


5

It's not necessarily true that attenuated vaccines are "preferable" to killed vaccines. It's a case by case basis. In some cases one or the other simply isn't possible or practical. It may not be possible to make a vaccine that's attenuated enough, for example. Or a killed vaccine may not be effective. Here are some pros and cons of attenuated vaccines: ...


5

One needs to be careful making broad generalizations about meningitis. The term simply refers to inflammation of the meninges (the outer layer surrounding the brain and spinal cord). Meningitis can occur due to a number of causes, most notably viral and bacterial infections, but can also also be due to fungi, parasites, toxins, cancer, etc. There is a vast ...


5

This is a great biological question! I'm glad we encourage such questions from curious people who want to learn more about modern biology. Much as other animals can be vectors for diseases that infect humans, plants can be vectors for pathogenic infectious agents. You may occasionally read news stories of disease-causing strains of Escherichia coli which ...


4

Between 1956 and 1977, 4 human cases of rabies virus infection were attributed to aerosolized rabies virus; Possible but very rare. https://academic.oup.com/jid/article/195/8/1144/816583


4

In the second figure – What does the color scale and color coding represent? Each color is an individual mosquito species, arranged the same from top to bottom on all plots. Here, on the left, all species are gathered on one plot, with the y-axis now labeled “Species.”   The sounds of many mosquitoes apparently have ...


4

The causative agent of the plague, Yersinia pestis, can be indirectly (via a flea vector) or directly (via exposure to infectious fluid or a bite) transmitted by rodents. In the western United States in particular, Y. pestis is endemic, and ground squirrels, prairie dogs, chipmunks, and woodrats are important reservoirs (see Cecil Medicine Ch. 320). US ...


4

Endemic and chronic/acute are unrelated properties of a disease. Endemic is a description of the frequency of a disease in a population or in an area. Chronic/Acute is a description of the state or course of a disease in an individual. For example, influenza is endemic in North America: the frequency goes up and down, there's always a few people who have ...


4

@Remi.b is correct that you haven't given us very much information, but I think we can reconstruct what's going on. Suppose the population growth rate is written out as $$ \frac{dN}{dt} = N ( b - \delta - \gamma N) $$ then the equilibrium (carrying capacity) occurs when $N>0$ and $dN/dt=0$, i.e. $b - \delta - \gamma K = 0$. Solving this for $K$ gives $(...


3

The place to find this information would be the Methods section of the paper. We spotted 33 µL of plasma spiked with HCVcc on the 24-well plates. They were either immediately tested for viable virus or stored at 4°C, 22°C, and 37°C for up to 6 weeks before testing. They tested their samples for (up to) 6 weeks. At the time of the 6th week they still ...


3

Yes. This has been possible since the 1990's. In the US recently, the flu vaccine was recently offered as a nasal spray. There is current research being done to aerosolize several vaccines. Public health officials have an interest in this method due to it being less expensive to produce, more people can receive the vaccine in a shorter time frame, and less ...


3

The picture is too blurry for an exact determination. From what I see it might be Metcalfa pruinosa or a related species, which is an insect of the order of the Hemipteri. It's a widespread parasite of ornamental plants. Here a page about it http://ag.udel.edu/research/delphacid/species/Metcalfa.htm if true, what you posted are the nymph, and you might be ...


3

This sort of thing happened to one of my plants. When I took a closer look at the plant, it was a group of white aphids. The brown coloration of the leaves of your cherry tree was relevant because aphids can sometimes kill the entire plant that they feed off of. I did not take a picture of the plant, but I found one online: https://entnemdept.ifas.ufl.edu/...


3

The only answer that makes numerical sense is 1. The product of two rates beta and delta (recovery * death) doesn't mean anything in SIR. And in answer three you're doubling the rate of infection (alpha). Looking at the other way, for R_0 it doesn't matter how people leave the Infected class, once you're either dead or recovered you no longer are ...


3

One might argue that since replication takes place in erythroblasts (Brown, Anderson, & Young, 1993), that it's not actually a respiratory infection either. Fluids are simply more hospitable to the virus and more transmissible. As for the rash, perhaps it is because the P antigen receptor that erythrovirus uses to infect erythroblasts is also ...


3

It's not that people didn't want to use hemagglutinin as a target for antivirals, it's that they haven't been able to get the antivirals through the approval process yet. There are a number of experimental inhibitors (see for example Progress of small molecular inhibitors in the development of anti-influenza virus agents) but the approval and licensing ...


3

Prophylaxis is typically prior to exposure. Condoms, for example, were historically referred to as prophylactics, in that they prevent pregnancy and many STIs. The reason the pre-exposure bit is given special attention in this context is that it refers to use of drugs with substantial risk of harm. Because of their associated risk, these drugs were ...


3

From the vantage point of other species, humans might be considered "bugs" in the sense that we are organisms that are causal in the ongoing extinction of numerous species. We're doing a pretty good job of it, so far: The included extinctions span numerous families of plants[4] and animals, including mammals, birds, amphibians, reptiles and arthropods. ...


3

Would it help to think a little differently? Rubber bands (for example) aren’t alive either, but there are several ways they can be destroyed, including physically pulling them apart or just by having them exposed to air enough. Viruses are the same, conceptually. Soap works in part by dissolving the layer of fat that keeps the virus together. It also ends ...


3

My question concerns the way that $d$ enters the SIR model, because I find it not so plausible: to consider all persons that are infected today and take a fraction $ν$ of them that will have recovered tomorrow. Well, it is in fact not very 'realistic' as you point out, but in the assumptions of the model, we see that the population has no ...


2

After V.cholerae gets into the human intestine it starts to multiply its numbers, and then becomes virulent after sufficiently expanding its numbers. This virulence drives the diarrhea which in part causes the bacteria to slough off into the intestinal lumen, and then into the external environment again. So in short it uses the human intestine to increase ...


2

It should be noted that many of the methods you talk about aren't necessarily for getting a number but rather a formula for $R_0$, all of which should be equivalent. However, when those methods step into the realm of getting a number by fitting parameters, they may give different results as they handle certain aspects of the data differently. You are ...


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