Emerging Viruses

Definition of emerging viruses:

Known viruses that have newly appeared in a human population and is rapidly increasing in disease incidence.

Source of emerging viruses:

    · Animals are usually the reservoirs of emerging viruses (zoonotic viruses).

    · Viruses were probably endemic at low levels in localized areas.

    · However, they could have “jumped” species, acquired a new host range and spread from there.

Examples of emerging viruses:

Dengue virus, Avian Influenza virus (e.g. H5N1 strain), SARS coronavirus, Nipah virus and Ebola virus.

http://bepast.org/docs/photos/nipah%20virus/nipah%20virus.jpg

Nipah Virus

http://m.blog.hu/li/lightscience/image/gpw-20050430a-fullsize-Ebola-virus-CDC-PHIL-ID-1181.jpg

Ebola Virus

http://ec.europa.eu/health/ph_threats/com/Influenza/images/influenza.jpg

Reasons for Emergence

Virus Factors

    · Spontaneous evolution of a new virus entity

    · Generation of a novel strain due to co-infection of different strains in an individual (random assortment)

Human Factors

    · Concentration of people with shared lifestyle

o E.g. the sharing of hypodermic needles, unsafe sex

    · Breakdown in public health

o Mainly in third world countries

    · Climate change

o E.g. increased wet seasons will lead to more stagnant water which might make it more conducive for mosquito breeding in a particular area. Aedes mosquito is a vector of dengue fever. Thus, the spread of the dengue flavivirus will be enhanced.

    · Man invading natural habitat of animal

o Deforestation for agricultural needs

o Closer to wild animals

o Increasing the possibility of zoonoses