biology

Human-to-human transmission

Human-to-human transmission is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Human-to-human transmission rather than just read about it. In short: Human-to-human transmission (HHT) is an epidemiologic vector, especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 203.9.

Key takeaways

Human-to-human transmission belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Human-to-human transmission to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Human-to-human transmission from memory before moving on to harder problems.

Reference excerpt

Human-to-human transmission (HHT) is an epidemiologic vector, especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 203.9. Interhuman transmission is a synonym for HHT. The World Health Organization designation of a pandemic hinges on the demonstrable fact that there is sustained HHT in two regions of the world.

Synopsis Relevant microbes may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, spraying of liquids, toilet flushing or any activities which generate aerosol particles or droplets or generate fomites, such as raising of dust. Transfer efficiency depends not only on surface, but also on pathogen type. For example, avian influenza survives on both porous and non-porous materials for 144 hours. The microbes may also be transmitted by poor use of cutlery or improper sanitation of dishes or bedlinen. Particularly problematic are toilet practices, which lead to the fecal–oral route. STDs are by definition spread through this vector.

List of HHT diseases Examples of some HHT diseases are listed below.

measles: vaccine available mumps: vaccine available chicken pox: vaccine available small pox bubonic plague: slim non-nil risk pneumonic plague: 1910-11 Manchurian plague tuberculosis Norovirus monkeypox SARS-CoV-1 SARS-CoV-2: vaccine available MERS Avian flu Sexually transmitted infections (STIs) or sexually transmitted diseases (STDs): Syphilis, aka French pox

Notes

References

Sources Cook N (2013). "10.1 Introduction; the role of fomites in the virus transmission". Viruses in Food and Water: Risks, Surveillance and Control. Cambridge: Woodhead Publishing. pp. 205–215. ISBN 978-0-85709-887-0. Larson EL, Liverman CT (2011). "Understanding the Risk to Healthcare Personnel: Fomite Persistence". Preventing Transmission of Pandemic Influenza and Other Viral Respiratory Diseases: Personal Protective Equipment for Healthcare Personnel: Update 2010. Washington: National Academies Press. p. 41. ISBN 978-0-309-16254-8.

Worked examples

Example 1 — a first encounter with Human-to-human transmission

Start with the simplest possible case. Write down what Human-to-human transmission claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Human-to-human transmission before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Human-to-human transmission ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Human-to-human transmission

In research: Human-to-human transmission appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Human-to-human transmission in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Human-to-human transmission is common in secondary-school and first-year university syllabi. It links to neighbouring topics Epidemics, Epidemiology, Global health, so understanding it makes those chapters shorter.
In everyday life: Look for Human-to-human transmission outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Human-to-human transmission in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Human-to-human transmission means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Human-to-human transmission out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Human-to-human transmission in simple terms?

Why does Human-to-human transmission matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Human-to-human transmission?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Human-to-human transmission.