49 votes
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Why is untreated trypanosomiasis invariably fatal in humans?

African trypanosomiasis, or sleeping sickness, is caused by the protozoan Trypanosoma brucei, a single-celled eukaryote. Being eukaryotic, it has a cell nucleus and a larger genome than most bacteria;...
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41 votes
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Why is it advised that infants are fed mother's milk?

The phrase "Breast is best" is a hotly debated one (source: The Guardian and personal communications with many folks). The reason why we don't want to feed infants cow's milk is, however, anything but ...
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38 votes
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Why don't we develop immunity against common cold?

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 ...
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  • 1,720
38 votes
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Why are scientists saying that the Omicron COVID-19 variant is a reason to get a booster?

(note: I'm simplifying things a bit here by only talking about antibodies; I don't mean to downplay other aspects of the immune response, just to keep it focused for a lay audience) Natural antibody ...
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  • 36k
30 votes
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What does vaccine efficacy mean?

Vaccine efficacy Pfizer's target measures for efficacy (see the study on clinicaltrials.gov) seem to be: Confirmed COVID-19 in Phase 2/3 participants without evidence of infection before vaccination ...
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  • 36k
29 votes

Are fully vaccinated people more likely to not get infected at all with COVID-19?

Yes, this is the effect of the vaccine. A reduction of infections of over 88%, a reduction of severe cases and death by 95% and higher. See reference 1 for the details. Data from the ReCoVAM Study ...
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27 votes

Why don't we develop immunity against common cold?

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 &...
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  • 4,089
25 votes
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Can fever cure Ebola disease?

Short Answer: Fever cannot cure Ebola simply because the virus is not temperature-sensitive. Background: Fever is a defense mechanism of the body which is specific to temperature-sensitive virus and ...
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21 votes

Why do doctors still advise HIV+ couples to wear a condom during sex?

Doctors would recommend the use of barrier protection for couples where both partners are HIV+ because the virus can mutate. Mutated forms of the virus can become resistant to Highly Active ...
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  • 4,945
20 votes
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Why does immunity from the flu vaccine appear only after two weeks?

Most information here can be found broadly in Cellular and Molecular Immunology, 8th Ed. Here's how the flu vaccine works: Scientists forecast months in advance which strains they think stand to ...
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  • 8,041
19 votes
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How Do White Blood Cells Learn? Or Do They?

So while some kind of a biological database might have been an evolutionary option, the way we evolved is different from this. Rather than 'planning' what diseases could be recognized in the ...
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  • 1,826
18 votes

Why can blood group O be given to all blood groups?

Good question! Let's start with an overview and explanation of the ABO blood grouping system (Dean, 2005): Blood groups, antigens and antibodies: Subjects with blood group A carry the A antigen on ...
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  • 51.1k
18 votes
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Why is an HIV infection considered "incurable"?

The reasons why HIV is "incurable" (a misnomer) are legion: HIV is a retrovirus, which means it inserts its own genome into the host cell's genome. You must therefore kill each and every infected ...
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  • 9,702
17 votes
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Why doesn't our immune system react to infused antibodies produced in a horse?

Our immune system does react to horse antibodies, but as with any adaptive immune response it takes some time for the response to develop. In the weeks before our immune response fully responds to the ...
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  • 14.1k
17 votes
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Is COVID-19 claimed to get less deadly over time? If so, why?

While the data are much too sparse and noisy to give an answer about what is happening to COVID-19's virulence (the technical term for the "deadliness" of an infectious disease), or to forecast what ...
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  • 4,846
16 votes
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What is the purpose of getting a rabies vaccine after exposure?

Rabies virus enters the body, typically from a bite, and then enters nerves which it follows up to the brain. An immune response to a first exposure of a pathogen generally takes many days, perhaps ...
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16 votes
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How do bats survive their own coronaviruses?

It's common for the reservoir host of a zoonotic virus to be tolerant of it. MERS coronavirus appears to cause mild or no disease in dromedary camels ( source ), but kills about 35% of confirmed ...
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  • 3,185
15 votes
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Can people with AIDS get a fever?

With AIDS, the whole immune system is not non-functional. The condition results in a severe drop in CD4+ T-cells, which is what primarily predisposes AIDS patients to secondary infections. Fever can ...
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  • 2,462
15 votes

Do spike-protein-based vaccines undermine the DNA repair system?

While the linked paper presents interesting results, the conclusions must be interpreted in context of their in vitro methods and cannot be readily extrapolated to understand the in vivo effect of ...
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  • 7,564
14 votes
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Septic Shock: I'll kill myself before you kill me

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 ...
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14 votes

Do spike-protein-based vaccines undermine the DNA repair system?

The authors explicitly suggest the first part of your question in their discussion section: indicating that full–length spike–based vaccines may inhibit the recombination of V(D)J in B cells, ...
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  • 3,185
14 votes

Why are scientists saying that the Omicron COVID-19 variant is a reason to get a booster?

Some Clarification: Scientist were not opposed to a third dose, they were opposed to the rich country getting a third dose before we vaccinated the rest of the world. The WHO is right to call a ...
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13 votes
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Why do people dying of immune deficiency diseases appear sick?

Many of the symptoms of disease are indeed related to inflammation, but inflammation depends heavily (though not solely) on the innate immune response. Patients with AIDS and some of the other ...
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12 votes
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What will happen if a foetus is Rh- and the mother is Rh+?

Nothing. Rhesus incompatibility results when people who are Rh- develop antibodies against Rh+ blood after exposure. People with Rh+ blood do not show any such reaction to Rh- blood. In a way, it's ...
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  • 2,227
12 votes
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Why are there 2 copies of RNA in the HIV virion?

You are not totally correct because these two strands don't have to be the same, they can be genotypically different, which occurs when a cell is infected by two distinct HIV strains. Also HIV uses ...
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  • 2,340
11 votes
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Why are people unable to develop lasting immunity against Norovirus?

So the direct mechanisms of norovirus immunity aren't well understood - the shortage of straightforward animal models, and the extreme difficulty in culturing the virus make mechanistic studies really ...
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  • 3,029
11 votes
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Is vermiform appendix no more a vestigial organ?

Short Answer: No, the appendix is still considered a vestigial organ. Long Answer: The idea that that vermiform appendix is vestigial originated when Kumar et al (1989) removed it from the body, but ...
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11 votes
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What are the difficulties/challenges against developing a coronavirus vaccine?

There are multiple challenges presented, and many of those are not limited to coronavirus vaccine. As mentioned above, it just takes time. Before a vaccine can be used in patients, clinical trials ...
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11 votes

What does vaccine efficacy mean?

It means protection against the virus brought to you by the vaccination. Around 45.000 people participate in the trial; 50% of these are vaccinated with the trial vaccine and 50% receive a placebo. ...
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  • 49.2k
10 votes
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If all B cells are present at birth, why should the primary response to an infection take longer than the secondary response?

These so called virgin B-cells (becase they never had contact with their antigen) which are present in your body only have random B-cell receptors (when secreted, these are the antibodies), mostly of ...
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