We’re rewarding the question askers & reputations are being recalculated! Read more.
56

Fever is a trait observed in warm and cold-blooded vertebrates that has been conserved for hundreds of millions of years (Evans, 2015). Elevated body temperature stimulates the body's immune response against infectious viruses and bacteria. It also makes the body less favorable as a host for replicating viruses and bacteria, which are temperature sensitive ...


35

Long lasting immunity is obtained by means of the adaptive immune system, and mainly involves the development of antibodies that identify specific parts (epitopes) of the pathogen's proteins. Common cold is typically caused by a type of virus called rhinovirus. Viruses have very high mutation rates, which alter the sequence of the virus proteins, modifying ...


26

There is one main answer to this question: The Zika virus spreads so fast because it never emerged in this part of the world. Hence there is no natural immunity available in the population and a lot of infections occur. Once this "first wave" of infections is over, the level within the population will fall drastically. Some more information on this topic can ...


23

In "Guns, Germs, and Steel" Jared Diamond includes quite a bit on this topic. His conclusion is that Europeans, and old world humans in general were much more exposed to their farm animals, often living in the same buildings. This allowed a much greater number of diseases to jump from animal to human, forcing us to development immunity against these ...


21

First, I want to note that ddiez has a good answer, but I thought this was good question to have a more expanded answer on immunology and pathogenesis. The First thing we need to establish what is a "cold". The most common cold is rhinovirus (HRV), but the second place holder is a little harder to define. For example, respiratory syncytial virus (RSV) ...


19

There is at least one important exception - it is generally thought that syphilis came to Europe from the Americas.


18

You can't catch conjunctivitis by looking at someone, but you can spread it around by touching your eye and touching something else, which then can pass the virus to someone else (viral conjunctivitis can be highly contagious). There are no hard facts, but one estimate is that people touch their faces an average of 3.6 times per hour, more if your eyes are ...


16

A mutation isn't necessary to explain the outbreak in the Americas, given the low immunity of the population, but there is tentative evidence that this strain of the Asian lineage of the virus may have developed some novel characteristics, which appear likely to have first emerged in the South Pacific. The virus in Brazil is very similar to the form that ...


15

Interesting question and hard to answer definitively. First of all: It seems still pretty clear that the major (and by far most important) infection route comes from direct contact with infected people or their body fluids and that aerosol transmission is of far less significance. Ebola is infecting cells of the immune system (mostly macrophages and ...


14

The important thing to recognize about the host response to sepsis is that it is actually a generalization of mechanisms used in local infection response by the innate immune system. When an animal has a local infection, such as at a wound site, innate immune cells such as monocytes and macrophages recognize 'generic' bacterial features, such as ...


12

The combination of these two reports from the CDC give information about the comparative prevalence of flu infection in the winter (September '12- May '13) and summer (May '13 - September '13). I'm going to assume that 2012-2013 was a fairly representative year as far as the level of detail of "do we get sick more in the winter" goes. Particularly striking ...


12

This really depends on the environment, one study (listed below as reference 1) found that the Ebola virus can survive under ideal conditions on flat surfaces in the dark for up to six days - see the figure from the same publication. However, the virus is quite sensitive to UV radiation (see reference 2 for all the details) and most viral particles are ...


11

Microwave ovens can indeed kill bacteria in food by heating them to high temperatures. For example, this article found that microwave heating could kill all of the Salmonella bacteria in a chicken thigh sample: The effect of microwave heating on Salmonella Enteritidis inoculated on fresh chicken was investigated using a microwave oven (800 w) to ...


10

There is both a set "list" of agents, but more importantly, a set of properties that an organism needs to be in order to be truly worrisome. First, the list: The CDC classifies agents into one of three categories, Class A, B, or C. Class A: These are organisms that are hard to control, highly transmissible, and lethal: Anthrax (Bacillus anthracis) ...


9

I have worked in hospitals (US) most of my life, treating both community-acquired, and more pertinently to this question, nosocomial (hospital acquired) infections, and have read many articles on the subject. I have never, ever seen ants mentioned anywhere. People, flies, cockroaches and rats, yes. Ants, no. However, ants are vectors in a few foreign ...


8

Nerve endings exist in a more or less homeostatic interstitial fluid medium which when disturbed in certain ways result in depolarization. This is a very simple explanation, but basically correct. Depending on the nerves being discussed, a change in the medium can be the presence/absence of neurotransmitters (serotonin, GABA, etc.), chemicals released from ...


7

Fever normally under hypothalamic heat center's control which stays at limbic system of brain . Hypothalamus sets its own set point 36.4-37.2 in healthy peoples by some molecules named exogenous and endogenous pyrogens, especially PGE2 ,TNF and IL1. The most important mechanism for fever is directing blood flow from skin to deep vascular pools and ...


6

The short answer is no, there is no minimum time between two colds. The reasons for this are different. Mostly it has to do with the viruses which cause the common cold. There is a bunch of them causing what we call a cold, including rhinoviruses, coronacviruses, adenoviruses, human parainfluenza viruses, human respiratory syncytial virus, enteroviruses ...


6

Ants can and do carry loads that are several times their own weight. I grew up in an area with a lot of ants, and a common scene was a long trail of ants acting as a food supply line. Once a morsel is located, they create a long feremone trail to that morsel. A large clump of ants is always working to break the food into smaller pieces, and several ants are ...


6

Hospitals have certain features: They are full of people immunocompromised in some way (old, exposed tissue, on steriods etc.) They are full of people with pathogens They are full of doctors who will give antibiotics to people with pathogenic infections This is a perfect breeding ground for drug resistance in pathogens, with lots of pathogens, lots of ...


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 ...


5

Bacteriophages are the only viruses where this phenomenon is called lytic and lysogenic cycle. There is a similiar phenomenon in humans (and other mammals as well) which is called "endogenous retrovirus" and is pretty common. For humans, there are estimations that something between 5 and 8% of the human genome are made of endogeneous retroviruses. See these ...


5

You are correct in that inflammation is a physiological process. It is vital for the correct development and localisation of a strong immune response, and contributes to tissue healing. However, the beneficial effects are replaced by dangerous processes when they are prolonged or too intense. This includes both effects of leukocyte attraction and invasion, ...


5

A virus does not typically destroy its host's DNA. Rather, the virus makes the host cell express viral proteins at an elevated rate compared to the host's own proteins. This is usually achieved because the viral genome contains a strong constitutive promoter, possibly coupled to an enhancer sequence. The virus may also preferentially insert itself into ...


5

First there is one major difference between HIV and TB: As long as the TB bacteria are still susceptible to treatment (which is developing into a major problem in some regions of the world) there is a effective treatment which can eradicate the infection. For HIV this is not possible. Here we can only lower the viral load (sometimes under the detection limit)...


5

The uninucleate sporozoites are injected by the mosquito into a human host. They mature in the liver parenchymal cells in schizonts. Each schizont releases into the blood flow 2,000 to 40,000 uninucleate merozoites. Each of them can infect a red blood cell. Here, a merozoite can release other 10 to 36 merozoites [1]. The numer of injected sporozites depends ...


5

Regrettably, I don't believe we know - we don't actually know why influenza is a seasonal disease in the first place. There are a number of possible theories, discussed in this review, but none of them are compelling enough to be a definitive causal explanation In terms of the difference between Influenza A and B, B mutates at a much lower rate, which may ...


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: ...


4

Yes, you can transmit HIV with infected needles/syringes. This is a quite common mechanism of transmission when drug addicts share and re-use needles and syringes and also in third world hospitals with poor hygiene standards. A drop of blood is considered infectious at least until it has completely dried up (some research showed that it might be contagious ...


4

No doubt influenza. The horizontal shift makes it very virulent and only a few mutations allow it to transfer from birds to mammals (as little as two). See here. There was a big push not to publish these as it would be so easy to make recombinantly. However, thanks to quick work, we have determined that our seasonal flu vaccine protects against this variant.


Only top voted, non community-wiki answers of a minimum length are eligible