Penyakit Infeksi: Aspek Laboratorium Influenza

From Molecular Virology to Clinical Decision Making

Mohammad Rizki
mohammadrizki@unram.ac.id

FKIK Universitas Mataram

2026-08-11

Influenza

Learning Framework

1

Virus structure

Menentukan fungsi HA, NA, M2, envelope, dan segmentasi genome.

2

Genome biology

Menjelaskan negative-sense RNA, 8 segmen, reassortment, antigenic drift/shift.

3

Replication cycle

Setiap tahap memberikan target diagnostik/farmakologis.

4

Host response

Menjelaskan mengapa pasien mengalami demam, myalgia, pneumonia, dan ARDS.

5

Clinical syndrome

Mengubah mekanisme menjadi diagnosis dan differential diagnosis.

6

Diagnosis

Menguji sensitivitas, spesifisitas, PCR, rapid test, dan clinical probability.

7

Treatment

Menghubungkan target molekuler dengan obat dan timing terapi.

8

Prevention

Menghubungkan antigenic evolution, immunity, vaksin, dan epidemiologi pandemi.

Why Influenza Remains Important?

A virus with two faces

Seasonal disease

  • Recurrent outbreaks
  • Moderate morbidity

Pandemic threat

  • Novel antigenic combination
  • Population susceptibility

Clinical Opening Case

The case

A 67-year-old man presents with:

  • Fever 39°C
  • Dry cough
  • Fatigue & severe myalgia

Symptoms began 24 hours ago.

History:

  • COPD
  • No vaccination this year

Question:

What pathogen is most likely?


Sudden onset systemic illness

Disease Pattern
Influenza Sudden
Common cold Gradual
COVID-19 Variable
Bacterial pneumonia Progressive

Virology Overview

Family: Orthomyxoviridae

Characteristics:

  • Enveloped
  • Negative sense RNA
  • Segmented genome

Why Negative Sense RNA Matters

  1. Negative RNA cannot directly function as mRNA.

  2. Therefore virus must carry RNA-dependent RNA polymerase into the virion.

Olympiad Question 1

A researcher removes viral polymerase from influenza particles.

What process is immediately impaired?

A. Viral attachment
B. Genome transcription
C. Viral budding
D. Capsid assembly

Catatan

B. Genome transcription

Because:

(-)RNA genome cannot be translated directly.

The virus must synthesize:

(-)RNA → (+)mRNA

Influenza Genome

8 RNA segments:

Encode:

  • HA
  • NA
  • M proteins
  • Polymerase proteins
  • Internal proteins

Why Segmented Genome Matters

Segmented genome allows:

Reassortment

Exchange of RNA segments between viruses.

Antigenic Shift Mechanism

Example:

Host:

Pig respiratory tract

contains:

  • Human influenza virus
  • Avian influenza virus

Co-infection occurs.

Olympiad Question 2

The emergence of a novel influenza subtype is most likely due to:

A. Point mutation in HA gene

B. Genome reassortment

C. DNA integration

D. Reverse transcriptase activity

Answer

B. Genome reassortment

This produces:

New HA/NA combination

→ little population immunity

→ pandemic risk

Influenza A Classification

Based on:

Hemagglutinin (H)

and

Neuraminidase (N)

Examples:

H1N1

H3N2

HA Function

Hemagglutinin mediates:

Virus attachment

by binding:

Sialic acid receptor

on respiratory epithelial cells.

Clinical Correlation

Antibodies against HA:

↓

Block viral entry

↓

Neutralizing antibodies

↓

Protection from infection