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Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.

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Viral diseases

i.e common (human) diseases caused by infection by a virus
- now including Ebola virus disease section at end
Disease -
Caused by
(Signs) and Symptoms
Control/
prevention
Spread by
Disease -
Common cold
(upper respiratory system infection) rhinovirus_3d_simulation (38K) Caused by
Rhinovirus (many forms)
and coronavirus (and others)
Image courtesy University of Melbourne
Signs and Symptoms:
Scratchy throat, sore throat, nasal congestion, runny nose, sneezing, (cough, fever) - more pronounced in young children
Control/
prevention
:
Cold medicines should relieve symptoms (lowering temperature, etc) but there is no vaccine
Spread by:
Airborne droplets (aerosols) from sneezes, coughs, etc or by contact -contagious for the first 2 to 3 days, usually not after the first week.
'
Disease -
Flu
(upper and occasionally lower respiratory system infection)
3d_influenza_transparent_no_key_full_180 (24K)
Caused by
Influenza virus

Image courtesy CDC
Signs and Symptoms:
Chill, fever, sore throat, muscle pains, headache, cough, fatigue, general discomfort
More serious than the (common) cold
Control/
prevention
:
  • Trivalent influenza vaccine (TIV) - needs reformulating each year as influenza virus evolves rapidly, and new strains quickly replace the older ones.
  • Antiviral drugs e.g. Tamiflu, Relenza) are quite effective.
  • Handwashing and disinfection of surfaces is also important.
  • Paracetamol may relieve symptoms e.g. fever and muscle aches.
Spread by:
Airborne droplets (aerosols) from sneezes, coughs, etc or by contact with contaminated surfaces
Disease -
Mumps mumps1874_lores (113K) Caused by
Mumps virus (a Rubulavirus)
Image courtesy CDC
Signs and Symptoms:
Swelling of salivary glands, headache, fever, inflammation of testes (more important in teenagers and adults)
Control/
prevention
:
Mumps vaccine (part of MMR and MMRV* vaccines)
Spread by:
Airborne droplets (aerosols) from sneezes, coughs, etc or by contact with surfaces

Very easily spread in university/college scenarios
Disease -
Measles
(also called rubeola, not to be confused with rubella) morbillivirus10707_lores (147K) Caused by
Morbillivirus
Image courtesy CDC
Signs and Symptoms:
Respiratory system infection, fever, cough, runny nose, red eyes, skin rash.
Control/
prevention
:
Measles vaccine (part of MMR and MMRV* vaccines)
Spread by:
Airborne droplets (aerosols) from nose and mouth, etc or by contact

Serious disease in some under-developed countries
Disease -
Rubella ("German measles") Rubella (36K) Caused by
Rubella virus
Signs and Symptoms:
Minor flu-like symptoms and rash but if a woman is pregnant it can cause deafness, eye abnormalities, and congenital heart disease in baby
Control/
prevention
:
Rubella vaccine (part of MMR and MMRV* vaccines)
Spread by:
Airborne droplet emission from the upper respiratory tract
Disease -
Chickenpox Varicella-zoster-virus (613K) Caused by
Varicella zoster virus
Also see below
Signs and Symptoms:
Skin rash, muscle pain, nausea, fever, headache, sore throat, pain in both ears, complaints of pressure in head or swollen face, and malaise in adolescents and adults
Control/
prevention
:
Varicella vaccine (part of MMRV* vaccines)
Spread by:
Airborne - coughing or sneezing or through direct contact with secretions from the rash.
Disease -
Shingles
Caused by
Varicella zoster virus reactivation after chickenpox infection - perhaps years before - virus travels down nerve to skin
Signs and Symptoms:
Painful, sensitive, tingling or burning skin, eventually turning into a rash of red spots, fever, headache and enlarged lymph nodes.
Control/
prevention
:
  • Antiviral medicines: acyclovir ACV (Zovirax)
  • Symptom control: Painkillers, calamine lotion against itching.
Spread by:
Shingles rash can spread chickenpox if touched so no sharing towels, swimming, or contact sports.
Disease -
(HIV/AIDS)
HIV (37K)
Caused by
Human immunodeficiency virus
Signs and Symptoms:
Progressive failure of the immune system allowing development of life-threatening opportunistic infections e.g. pneumonia and cancers
Control/
prevention
:
  • Use of condoms (protected sex)
  • (new) disposable syringes and needles
  • multiple antiviral treatment now much more effective at extending life expectancy, but not preventing infectiousness
  • screening of blood and products
  • no vaccine
Spread by:
Transfer of body fluids: blood, semen, vaginal fluid, pre-ejaculate, or breast milk

Using non-sterile syringe needles (drug addicts or insecure health service)
Disease -
(HPV) HPV (36K) Caused by
Human papillomavirus
Signs and Symptoms:
Small genital and other warts: may be insignificant (both sexes)
- may lead to cancer within the reproductive system, especially cervical cancer in females (major cause of cervical cancer)
Control/
prevention
:
  • HPV vaccine - now administered to teenage girls in UK and USA - not effective against existing infections
  • condoms
  • microbicides
Spread by:
Sexual activity, including oral sex
Disease -
Oral Herpes
Genital Herpes

(other forms) herpes (8K) Caused by
Herpes simplex virus
Signs and Symptoms:
Blisters (cold sores) on lips, genitals (other parts of the body may be infected)
Control/
prevention
:
Condoms
antivirals: acyclovir ACV (Zovirax)
Spread by:
Skin-to-skin contact especially with active lesion or body fluid
Infection remains and can be reactivated (depending on health?)
* not normally given in UK

Things to research

How common is the common cold?

How much worse are smokers affected with colds than non-smokers?

(In the context of influenza) What is the difference between an epidemic and a pandemic?

What does H5N1 mean?

Avian (bird) flu

Swine flu

Past outbreaks of flu (often with geographical associations)

Death rates from these diseases in the western world and in developing countries.

Vaccination rates against these diseases in the westerm world and in developing countries.

Incidence of mumps before and after vaccine development (1967? and MMR 1988), and since 1988 when doubts about the MMR vaccine were raised by Andrew Wakefield - now discredited.

% coverage (immunisation) of population over this time

Find out if you have had the MMR vaccine (and the follow-up booster shot).

Measles - mortality in UK/ USA and in sub-Saharan Africa

There are many other human viral diseases.
Find out about one that has a name that starts with the same letter as your surname!


Web references

Measles cases at '18-year high'


Ebola Virus Disease (EVD)

I have produced this section in response to the recent events in western Africa (Liberia, Sierra Leone and Guinea) and the media attention given to infected health workers and ordinary travellers returning from this area. And there are ongoing developments in other parts of the world ....
Disease - Ebola Virus Disease (EVD)

Caused by
Ebolavirus (EBOV) - named after the Ebola River in the Democratic Republic of the Congo (formerly known as Zaire), the location of the first known outbreak (in August 1976)
PHIL_1832_lores (42K)
Image courtesy CDC

The virus particle has an unusual shape.


Signs and Symptoms:
Ebola is a haemorrhagic fever, i.e. it causes high temperature and the escape of blood - internally or externally. Some symptoms may initially resemble influenza, "stomach bugs" or malaria, but they then develop into a more serious phase.

Symptoms of Ebola include
Symptoms may appear anywhere from 2 to 21 days after exposure (average 8-10 days).

It is thought that sufferers are infectious (i.e. can pass on the disease in body fluids) from the time symptoms appear, but these devlop gradually. The CDC says that Ebola is only contagious if the person is experiencing active symptoms.

In survivors, the virus may remain in parts of the body which are not subject to the protection of the immune system: the eyes, brain and spinal cord. It may be latent for some time, and in some cases cause meningitis (inflammation of the membranes surrounding the brain and spinal cord).

Similarly, it has been found that some male survivors produce virus particles in their semen for some time. Unprotected sex may therefore spread the virus.

Control/prevention:
Recovery from Ebola depends on good supportive clinical care and the patient’s immune response.

Oral reydration therapy (dilute solution of sugar and salts, taken by mouth) or intravenous therapy (similar solution, from a 'drip') are helpful.

In a community context Ebola cases need to be identified, isolated and treated. Possible contacts need to be traced, and treated in order to break the chains of transmission. Health care workers must strictly follow infection control (barrier nursing) in hospitals [or substitute buildings]. Safe burial practices may differ from traditional methods. It is better to check travellers before (or during?) flight than on arrival.

Specific chemical treatments for Ebola have not undergone some of the usual testing procedures. It may be said that the development of these drugs are subject to different economic and scientific influences in Africa and the western world.

Several chemicals seen as candidates for treating Ebola have been fast-tracked. Their potential side-effects and the lack of randomised clinical trials have been sidelined in the light of the perceived risks of Ebola.

Certain anti-viral drugs approved for other viral infections have been used in the treatment of Ebola, mostly in Africa, but it is difficult to compare their effectiveness as conditions are not standardised.

One possibility is the experimental drug ZMapp which is based on a combination of three monoclonal antibodies, aimed specifically at Ebola proteins.

There is at present no vaccine against Ebola, although some have been through 2 stages of testing in Africa, but this has stalled because large numbers of volunteers are needed for the next stage of testing. It has been suggested that blood serum from those who have survived an Ebola infection may be effective. People who recover from Ebola infection develop antibodies that last for at least 10 years.

Spread by:
Mainly by direct contact of the outer surface of the human body: skin (possibly damaged), eyes, nose, or mouth (mucous membranes) with blood or body fluids (urine, saliva, sweat, faeces, vomit, breast milk, or semen) from an infected individual.
Everyday social practices - handshakes etc - can cause widening of its spread in epidemic situations.

Transfer can also take place in a hospital setting via hypodermic needles and scalpel blades ("sharps") - sometimes re-used in certain circumstances.

Outbreaks are thought to have originated from wild (African) animals such as fruit bats and bushmeat - including monkey.

* It is not spread via the air by droplet infection. *

The virus is deactivated by normal disinfectants but it may be easily spread by sloppiness in hygiene.

Full (disposable) protective clothing including face masks is required for healthcare and associated personnel including those disposing of bodies, and this may be a special problem in hot conditions (especially when being removed).

Ebola Web Links

CDC. Centers for Disease Control and Prevention. CDC 24/7: Saving Lives. Protecting People.

Ebola (Ebola Virus Disease) CDC update

Ebola virus disease From Wikipedia, the free encyclopedia

Ebola virus epidemic in West Africa

History in the making:

Ebola: The First Glimpse of a Virus

News:

Ebola screening begins at Heathrow airport

BBC News Africa items:

Why Ebola is so dangerous

I caught Ebola in Guinea and survived

Ebola vaccines left hanging as GSK, Merck, J&J scramble for trial volunteers


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