Definition and characteristics
An epidemic is then unusual increase in the number of cases of an infectious disease which already exists in a certain region or population. It can also refer to the appearance of a significant number of cases of an infectious disease in a region or population that is usually free from that disease.

Epidemics may be the consequence of disasters of another kind, such as tropical storms, floods, earthquakes, droughts, etc. Epidemics may also attack animals, causing local economic disasters.

In general, the Red Cross Red Crescent response to epidemics prioritizes creating awareness, advocating effective action, social mobilization based on volunteer activities and logistics support (transport, warehouses, etc). Federation support often complements the efforts of UN bodies.

Avian flu
Avian influenza (AI) is a viral infection primarily affecting birds (chickens, ducks, geese etc., both domestic and migratory species), but also sometimes other species such as pigs and tigers.

Rarely, bird flu can cause severe infections in humans. There are many different strains or varieties of AI viruses. They are a sub-group of influenza viruses, which includes the flu virus that causes seasonal outbreaks in humans around the world every year.

Cholera
Cholera is mainly spread by drinking water contaminated by faeces. The fatality rate for severe, untreated cases is 50 per cent; when treated this drops to one per cent.

The incubation period is 1-12 days and severe cases need hospitalisation. Less severe cases can be treated with rehydration therapy on an outpatient basis. Only 10 per cent of those infected present symptoms.

Key control factors are: ensuring a safe water supply and rigorous hygiene (hand washing and disposal of soiled items).

Crowded wards are not a hazard to staff or visitors, if good hygiene is observed. Quarantine is unnecessary. Vaccine is inappropriate in an emergency.

Dengue fever
Dengue or breakbone fever and dengue haemorrhagic fever are transmitted by "day biter" mosquitoes. Dengue fever is rarely fatal; the haemorrhagic variety, if untreated, can result in a 40-50 per cent mortality rate. With hospital care and fluid therapy, this can be brought to below five per cent.

No vaccine or specific treatment is available. Epidemic control measures comprise mosquito destruction and elimination of breeding sites and the use of mosquito repellents by exposed persons.

Ebola and Marburg
Two distinct viral diseases with similar symptoms. Both have a high fatality rate (up to 90 per cent for Ebola) and are extremely contagious - transmission is through contact with all body fluids and organs, use of contaminated needles and syringes, and the aerosol route.

Extraordinary precautions should be taken to prevent contamination of all those involved in assisting patients. The reservoir of the two viruses is unknown.

Malaria
Malaria is transmitted by the bite of the anopheles mosquito, a dusk to dawn biter.

Where the disease is endemic, the local population has some degree of immunity. The people at greatest risk are those from a non-malarial area, such as IDPs or refugees. They can be protected by a weekly dose of a malaria suppressive drug. Of the four types of malaria, falciparum can be rapidly fatal and needs prompt treatment.

Treatment is by orally administered drugs. Control measures include the spraying, filling or draining of standing water where mosquitos breed, the spraying of living and sleeping quarters and the use of bednets. Quarantine is unnecessary, as is the immunisation of contacts. An immunisation coverage of less than 90 per cent means a major risk of outbreaks.

Measles
This is a highly communicable viral infection that can result in a very high mortality rate, especially among children and undernourished populations.

A prompt and comprehensive vaccination programme at the start of an outbreak can help limit its spread. If vaccine supplies are limited, the first priority is malnourished and hospitalized children, the next priority six-month to two-year-old children. A reliable cold chain is essential for vaccine storage. Isolation or quarantine is impractical.

Meningococcal Meningitis
Meningococcal Meningitis is an acute bacterial disease. Epidemic waves occur at irregular, unexplained intervals. Chiefly affects children and young adults, especially those in crowded living conditions.

The disease is transmitted by direct contact with nose and throat discharges. Infected individuals should be separated from others and their immediate contacts put under close health surveillance.

Rapid treatment, with penicillin or ampicillin, is essential. Emergency immunization campaigns are reasonably effective.

Yellow fever
Yellow fever is a deadly and fast-spreading mosquito-borne virus occurring only in parts of Africa and South America. The disease is highly communicable.

Action to control an epidemic should include mass vaccination of people at risk; screening and spraying of patients' rooms or hospital wards to prevent mosquito access; elimination or use of larvicide on all existing or potential mosquito breeding sites; spraying with insecticide of all houses in the community. Vaccination provides a ten-year immunity.

HIV/AIDS
HIV/AIDS (Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome) will kill more people this decade that all the wars and disasters in the past 50 years. Since the AIDS epidemic began, 25 million people have died and more than 40 million are now living with HIV and AIDS. In 2001 alone, five million people became infected worldwide.

Epidemic diseases are not new but what sets HIV/AIDS apart is its unprecedented negative impact on the social and economic development of nations. Everyone, rich or poor, young or old, is affected by the HIV/AIDS epidemic but people in developing countries, particularly young women, are the most vulnerable. The majority of the victims are adults in the prime of their working and parenting lives. Their legacy is a decimated workforce, fractured and impoverished communities, and millions of orphans.

While 70 per cent of HIV-infected people live in sub-Saharan Africa, AIDS is a global problem. In countries like Zimbabwe and Botswana, over 25 per cent of people between the ages of 15-49 are infected with the virus. HIV infection is also spreading rapidly in south and south-east Asia, the countries of the former Soviet Union and the Caribbean.

AIDS can be prevented. The fight against the disease must be waged at the local level. Individuals and communities can cope with the spread of HIV/AIDS by being properly informed, assessing accurately the factors that put them at risk of infection and by subsequently acting to reduce those risks. The problem, according to the World Bank, is that there has not been sufficient amount of coordinated activities to slow and eventually reverse the spread of the disease. Individuals, governments, civil society, private sector groups, international and non-governmental organizations must fully commit and participate in scaling up response ensuring that complementary initiatives occur at the national and regional level.

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