Influenza

Influenza is acute highly disease that shows endemic,epidemic and pandemic spread.

Causative organism:
Type A:responsable for epidemics and pandemics and may show mutation changes.
Type B: may cause outbreacks in confined groups and is less lieble to mutation.
Type C: causes sporadic cases,usually of mild or inapparent disease.

Reservoirs of Infection:
Man: cases where the virus find exit in respiratory discharges,from the mouth and nose.They are infectious for few days.
Animals: pigs,horses and some avian species are reservoirs of subtypes of virus A.

Modes of Transmission:
-direct droplet infection: the most important
-airborne infection with crowded groups (schools,camps)
-freshly soiled articles and fomites.

Incubation period: 1-3 days.
Caracteristics: manifestations and severity vary,may be inapparent,mild,typical or severe fatal disease.Uncomplicated disease is self-limited,of 2-7 days.

Typical cases: abrupt onset,with high fever,chills,headache,myalgia and respiratory catarrh (sore throat,coughing).

Complications:
-secondary bacterial infection of respiratory tract,usually streptococcal or pneumococcal,causing acute sinusitis,otitis media,bronchitis and pneumonia.
-Viral pneumonia,by influenza virus (rare).
-Pericarditis,myocarditis and thrombophlebitis (uncommon).

An individual may get more than one influenza attack,due to:
-many types and subtypes of influenza virus
-continual antigenic changes of the virus.

Age incidence: age group 5-15 years shows the hight incidence.

Prevention:
Adequate ventilation and spacing in confined and public places are generally required,yet they are not significantly effective to prevent spread of outbreaks and epidemics once started.
And by active immunization principally.