The rhinovirus is one of the many viruses that can cause the common cold

Viruses are infectious micro-organisms that require a living host to survive and multiply. When one enters your body, it invades and takes over cells, redirecting them to produce more of the virus.

How do our bodies defend us from viruses?

When our bodies come under attack from a viral infection they launch a sophisticated defence known as ‘the immune response‘. Our immune system is designed to recognise the cells that make up our bodies and repel any foreign invaders such as viruses.

They do this by using a huge army of defender cells which consist of different types of white blood cell. We make around a billion of them every day in our bone marrow.


How HIV/AIDS overwhelms the body


HIV attacks and kills a type of immune system cell known as T lymphocytes. These T cells are crucial for killing other cells in the body that have been infected with germs.


Without T cells, other immune system cells, such as antibody-making B cells, can’t work properly.


If HIV is not treated the number of T cells drops steadily. Eventually, numbers fall to the point that the risk of infection greatly increases. This end-stage is known as AIDS.



White blood cells called macrophages destroy germs as soon as they detect them. However, if a viral infection begins to take hold we fight back using a more powerful defence of white cells called T and B lymphocytes.


Antibodies are a special protein made by B cells. They bind to a virus to stop it from replicating, and also tag viruses so that other blood cells know to destroy them.


T cells have different roles to play. Some act as guard dogs that raise the alarm when they detect invading viruses; others kill virus-infected cells directly, or help B cells to produce antibodies.


Once the virus has been cleared, a small number of these specialist B and T cells persist and retain an accurate memory of the destroyed virus.


This means our immune systems are primed to prevent another infection from the same virus, without attacking the body’s own cells by accident. This is known as ‘acquired immunity‘. Having a single infection with mumps during childhood will give you lifelong resistance, for example.


Scientists have harnessed this natural ability in order to create vaccines, which use dead or weaker strains of viruses to prime the immune system and stimulate long-term resistance without causing the actual infection.


Childhood immunisation programmes against highly infectious viruses, such as measles, are particularly important as these infections can cause serious and even fatal complications first time around.


Why do viruses come back?


Firstly, manyviruses like those that cause fluare skilled at rapidly mutating as they replicate. Each new virus has small, but often advantageous changes, in its genes and these accumulate as the virus passes from one person to another.


During this process, the virus alters its appearance and our immune memory cells struggle to recognise it, leaving the virus free to infect us once more.


This is why you can keep catching the flu – new mutated strains constantly develop, which the immune system can’t detect.


The flu virus also has the advantage of being able to infect a variety of hosts, from humans to birds to swine. The strains become very different during their transmission within animal groups. This makes them unrecognisable to the immune system and, on the rare occasion when they jump back to humans, they can spread rapidly.


Unlike the flu, colds are not caused a single type of virus but any one of hundreds of different types of virus that can infect the upper airways. These viruses don’t mutate like the flu viruses, so with each cold the immune system becomes resistant to the virus that caused it. However, people will still get recurrent colds simply because they keep coming across new viruses they haven’t had before.


Other viruses, such as the chickenpox virus, become inactive before they are destroyed by the immune system. They remain dormantin our bodies but can be reactivated in later life by physical and emotionalstress, resulting in a condition called shingles. One in 10 people who have chickenpox as children will have shingles as adults.


Another technique – one used by the herpes simplex virus which causes cold sores – is to hide from the immune system in nerve cells called neurones. When the virus is activated by hormones or stress on the neurones, it leaves itshost neurone cells intactbut travels down the nerve to the skin. Here it destroys skin cells and forms blisters on the lips which discharge the virus.


Scientists have suggested that this is an evolutionary survival tactic for the virus. It detects changes in the body which could threaten its existence, and moves to the skin causing a superficial eruption, liberating virus particles to find a new, healthy host.


Will we ever find a cure for the common cold?


Progress is being made in creating an antiviral drug that could kill multiple viruses, in the same way that antibiotics kill many different types of bacteria.


At present, antivirals are tailored to specific diseases such as HIV and hepatitis. But a team from the Massachusetts Institute of Technology have created one that has successfully treated15 different viruses in lab tests on human tissue and mice.


It was created by ‘wiring together‘ two natural proteins – one that detected virus entry, and another that acted as a suicide switch that kills the infected cell.


The drugs have yet to be tested on humans. For now, the research continues.


taken with kind permission from

 lesson prepared by Angloland skola ||


Words and definitions

to cause – to bring about

common cold – the common cold is a viral infection of your upper respiratory tract — your nose and throat. A common cold is usually harmless, although it may not feel that way at the time. If it’s not a runny nose, sore throat and cough, it’s the watery eyes, sneezing and congestion — or maybe all of the above. In fact, because any one of more than 100 viruses can cause a common cold, signs and symptoms tend to vary greatly.

microorganism- an organism of microscopic or submicroscopic size, especially a bacterium or protozoan.

to defend – to fight off , to stave off , to keep off, to hold off, to keep away

Immune response -a system of biological structures andprocesseswithin anorganismthat protects againstdisease. To function properly, an immune system must detect a wide variety of agents, fromvirusestoparasitic worms, and distinguish them from the organism’s own healthytissue.

to repel  – to put off, to eliminate, to get rid of

bone marrow –the flexibletissuein the interior ofbones.. On average, bone marrow constitutes 4% of the total body mass of humans

to overwhelm-a .  to defeat completely and decisively  b.To affect deeply in mind or emotion: 3.To present with an excessive amount:

germs – microorganisms causing diseases

properly – well done, done in a proper way

antibody –also known as animmunoglobulin(Ig), is a large Y-shaped proteinproduced byB cellsthat is used by theimmune systemto identify and neutralize foreign objects such asbacteriaandviruses. The antibody recognizes a unique part of the foreign target, called anantigen

macrophages any large phagocytic cell occurring in the blood, lymph, and connective tissue of vertebrates

to take hold – to grab, to catch, to capture

lymphocytes –type ofleukocyte(whitebloodcell) that is of fundamental importance in the immune systembecause lymphocytes are the cells that determine the specificity of the immune response to infectious microorganisms and other foreign substances. In humans lymphocytes make up 25 to 33 percent of the total number ofleukocytes. They are found in the circulationand also are concentrated in central lymphoid organs and tissues, such as the spleen,tonsils, andlymph nodes, where the initial immune response is likely to occur.

to bind – to tie together, to fasten, to secure , to confine, restrain, or restrict as if with bonds

to replicate – to duplicate, copy, reproduce, or repeat.

to tag – to label, identify, or recognize with or as if with a tag

guard dogs – a large aggressive dog trained to guard persons or property; watchdog

to raise the alarm – to alert, to warn

to detect – to find, to identify

to retain- to keep 
accurate – precise, exact

to prime  to make ready; prepare

acquired immunity – Immunity obtained either from the development of antibodies in response to exposure to an antigen, as from vaccination or an attack of an infectious disease, or from the transmission of antibodies, as from mother to foetus through the placenta or the injection of antiserum.

mumps –  a disease caused by a virus that usually spreads through saliva and can infect many parts of the body, especially the parotid salivary glands. These glands, which produce saliva for the mouth, are found toward the back of each cheek, in the area between the ear and jaw. In cases of mumps, these glands typically swell and become painful.

lifelong – while the person is alive , for ever

resistance power or capacity to resist;especially:the inherent ability of an organism to resist harmful influences (as disease, toxic agents, or infection)

to stimulate – to motivate

to harness – to curb, to stop, to control

to prime – to make somebody or something ready, to prepare , to become prepared for future action or operation

measles – an acute, contagious viral disease, usually occurring in childhood and characterized by eruption of red spots on the skin, fever, and catarrhal symptoms. Also measles.

immunization programmes

first time round – for the first time something has appeared or occurred somewhere

flu – influenza

skilled at – good at , expert in , apt

to mutate –to undergo or cause to undergo mutation

mutation – a change of the DNA sequence within a gene or chromosome of an organism resulting in the creation of a new character or trait not found in the parental type.

b.The process by which such a change occurs in a chromosome, either through an alteration in the nucleotide sequence of the DNA coding for a gene or through a change in the physical arrangement of a chromosome.

advantageous – beneficial, useful , offering or producing advantage

to alter – to change

appearance – looks , the way something looks

strain- ageneticvariant or subtype of a micro-organism (e.g.virusorbacteriumorfungus). For example, a “flu strain” is a certain biological form of theinfluenzaor “flu” virus.

host- 1. one who receives or entertains guests in a social or official capacity. 2. the animal or plant on which or in which another organism lives.

swine – pig, hog

transmission – the spread of viruses from one body to another

to spread – to scatter, to disperse, to distribute, to take up a larger area or space; toexpand, be extended

the upper  airways –  theupper respiratory tractorupper airwayprimarily refers to the parts of the respiratory systemlying outside of thethorax[1]or above the sternal angle ( nose, nasal cavity, paranasal sinuses, pharynx

resistant –opposed to something : wanting to prevent something from happening. : not affected or harmed by something

recurrent occurring often or repeatedly.

to come across – to encounter by chance and suddenly

chickenpox virus –chickenpox causes a rash and can make a child feel generally unwell. Treatment aims to ease symptoms until the illness goes. Full recovery is usual in children. Serious complications are rare but are more likely to occur in children with a poor immune system, such as those on chemotherapy.

dormant – sleeping, inactive , not showing signs of life

physical and emotional stress

shingles –herpes zoster(or simplyzoster), commonly known asshinglesand also known aszona, is aviral diseasecharacterized by apainfulskin rash withblistersin a limited area on one side of the body (left or right), often in a stripe. The initial infection withvaricella zoster virus(VZV) causes the acute, short-lived illnesschickenpoxwhich generally occurs in children and young adults. Once an episode of chickenpox has resolved, the virus is not eliminated from the body and can go on to cause shingles—an illness with very different symptoms—often many years after the initial infection.

herpes simplex (“creeping” or “latent”) is aviral diseasefrom the herpesviridaefamily caused by bothHerpes simplex virustype 1 (HSV-1) and type 2 (HSV-2). Infection with the herpes virus is categorized into one of several distinct disorders based on the site of infection.Oral herpes, the visible symptoms of which are colloquially calledcold soresorfever blisters, is an infection of the face or mouth. Oral herpes is the most common form of infection.Genital herpes, known simply asherpes, is the second most common form of herpes. Other disorders such asherpetic whitlow,herpes gladiatorum,ocular herpes, cerebral herpes infectionencephalitis,Mollaret’s meningitisneonatal herpes, and possiblyBell’s palsyare all caused by herpes simplex viruses.

cold sores-sometimes called fever blisters, are groups of small blisters on the lip and around the mouth. The skin around the blisters is often red, swollen, and sore. The blisters may break open, leak a clear fluid, and then scab over after a few days. They usually heal in several days to 2 weeks.

neurons –a neuron is a nerve cell that is the basic building block of the nervous system. Neurons are similar to other cells in the human body in a number of ways, but there is one key difference between neurons and other cells. Neurons are specialized to transmit information throughout the body.

to leave something intact – to leave untouched, pristine

blisters –  a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid calledserumorplasma.[1]However, blisters can be filled withblood(known asblood blisters) or withpus(if they become infected).

to discharge the virus – to release

evolutionary survival tactic – survival skills are often basic ideas and abilities that ancient humans have used for thousands of years.

at present – now, at the moment, currently

tailored – made to measure

hepatitis  amedical conditiondefined by the inflammation of the liverand characterized by the presence ofinflammatorycellsin thetissueof the organ. The name is from the Greekhepar(παρ), the root beinghepat– (πατ-), meaningliver, and suffix-itis, meaning “inflammation” (c. 1727).The condition can be self-limiting (healing on its own) or can progress tofibrosis(scarring) andcirrhosis.

tissue –a part of an organism consisting of a large number of cells having a similar structure and function

successfully treated – healed and cured in medical terms

wiring together –to bind the pieces of something together with wire; to bind things together with wire or so fasten as if by wire

entry –an act of going or coming in.

research – survey, analysis , scrutiny

taken with kind permission from

lesson prepared by Angloland skola ||