Internal Medicine

0521779407-10 CUNY1086/Karliner 0 521 77940 7 June 7, 2007 18:40

Influenza 833

Influenza..........................................

CAROL A. GLASER, MD

history & physical

History

■3 types of flu virus recognized: A, B, C

➣A includes 3 subtypes: H1N1, H2N2, H3N2

➣A subtypes – classified by antigenic properties of surface glyco-

protein – hemagglutinin (H), neuraminidase (N)

➣Type A associated with widespread epidemics/pandemics

➣Emergence of completely new subtypes occurs at irregular inter-

vals, only with A responsible for pandemics

➣Type B – infrequently associated with regional or widespread

epidemics

➣Type C – usually sporadic cases, minor localized cases

■Human host

■Transmitted airborne (especially enclosed spaces) and direct contact

■Short incubation period (1–3 days)

■Highly contagious

■Highest incidence in winter

Signs & Symptoms

■Sudden onset of fever, frequently with headache, myalgia, prostra-

tion, coryza, sore throat and cough

■Cough often severe

■Occasionally GI tract manifestations (nausea, vomiting, diarrhea),

especially in children

■Manifestations other than cough usually limited 2–7 days

tests

During Early Febrile Stages:

■Antigen detection (DFA or ELISA) in respiratory secretions sensitive,

widely available

■Isolation of virus in respiratory secretions is also good test

■Nucleic acid methods (e.g., PCR) available in some settings

■Serology of limited utility in acute setting, confirm infection with

acute and convalescent bloods