Mental health articles

infectious disease characteristics Infectious diseases are caused by a variety of biological agents such as viruses, bacteria, fungi, parasites and
their toxic products. They arise through transmission
of the agent from an infected person, animal, or reservoir
to a susceptible host where they trigger a pathological
reaction. In contrast to non-communicable diseases,
the population dynamics for infectious diseases
are particularly influenced by the transmission patterns
between infected persons or animals and exposed susceptible
individuals.
Basic Characteristics infectious disease characteristics

In developed countries, a higher prevalence of infectious
diseases can be observed among migrant populations
compared to the native population. This is due
to the fact that migrants often come from developing
countries where infectious diseases are still rampant.
There, infectious disease accounts for approximately
44% of overall mortality and substantial morbidity,
a finding that has remained almost constant over
the last decades (World Health Report 2004). This burden
of disease includes also the sequelae of chronic
infectious diseases such as cancer (e. g. hepatocellular
carcinoma as a consequence of chronic hepatitis B
or hepatitis C infection). In addition to sick individuals,
healthy persons are also of great importance for
the transmission dynamics in populations. They sometimes
carry the infection without knowing (carriers) and
may thus transmit it to susceptible individuals. Infections
also represent an underestimated threat for people
who travel from the Northern hemisphere to the developing
world, be they migrants or tourists.
Examples of infectious diseases which contribute significantly
to the burden of disease in migrant populations
include tuberculosis, diarrhoeal diseases of various
origin as well as hepatitis A, B and C. Further
examples are vector-borne diseases such as malaria
and dengue, sexually transmitted infections (HIV/Aids,
syphilis, Chlamydia infections, hepatitis B, human
papilloma virus infection) and Helicobacter pyloriassociated diseases .

Migration from developing to developed countries
bears opportunities as well as risks (epidemiological
transition) for persons. Better management and treatment
of infectious diseases in developed countries
make it possible for known or newly diagnosed infections
to be effectively treated. Where this occurs, the
incidence and prevalence of acute infectious diseases
such as malaria and hepatitis A in migrant populations
may reach levels similar to those in the native population.
However, it is possible that during visits to the
country of origin, individuals again become exposed
to infectious agents with a high local prevalence. They
may thus acquire the infection and import it to the country
of destination. We then observe an increase of incident
cases and possibly outbreaks in the migrant population.
In the case of chronic infections, a substantially
high level of endemicity will remain even after
long periods of residence in the country of destination.
This may be the case for several chronic infections like
tuberculosis, HIV/Aids, and hepatitis B and C. Possible reasons are: 1. the infection is not diagnosed and therefore not treated. 2. The infection is treated, but insufficiently so. 3. Effective treatment for the infection
is not available in spite of a correct diagnosis. 4. Social disparities prevent access to adequate health care.

Tags: disease, infectious disease