The Sealed Nectar

Scenario: Pandemic Preparedness

A patient came. After performing physical examinations, blood test, chest radiograph and viral examination, the doctor suspect that this patient suffer a serious viral infectious disease that may spread to community. After reporting to municipal health agency, the agency performs an outbreak and pandemic preparedness measures. Before this incidence, WHO has already declares several emerging and reemerging diseases that occur due to genetic evolution of viruses.

INFLUENZA

Influenza A, B and C all have segmented genome. The two major proteins of influenza are the surface glycoprotein - haemaglutinin (HA) and neuraminidase (NA). HA is the major antigen for neutralizing antibodies and is involved in the binding of virus particles to receptors on host cells. Pandemics are a result of novel virus subtypes of influenze A, created by reassortment of the segmented genome (antigenic shift), whereas annual epidemics are a result of evolution of surface antigens of influenza A and B virus (genetic drift). NA is involved in the release of progeny virions from the cell surface and prevents clumping of newly formed virus. (Epidemiology and pathogenesis of influenza, Maria C. Zambon, 1999)

Type A and B influenzaviruses regularly cause outbreaks of respiratory disease and general malaise during winter and spring in large parts of the world’s population. Influenzaviruses have a wide animal reservoir, and, by the mechanism of reassortment, animal type A influenzaviruses have contributed genes, for instance coding for the haemagglutinin (HA) H3, to viruses which became human pandemic viruses.

It has been shown that human H1N1 and also H3N2 influenza A viruses can infect pigs, and, vice versa, that related pig viruses can infect humans. By contrast, avian influenzaviruses, representing by far the biggest diversity and reservoir of influenza A viruses, were thought to circulate only within their original host or closely related species. Contribution of avian genes into viruses able to replicate in humans was thought to be possible only by reassortment, with pigs being the likely host, as these animals were shown to replicate avian influenzaviruses to a certain extent (“mixing vessel” theory of Scholtissek et al.136; Scholttissek and Naylor137).

How is flu spread?

The flu virus is spread from person to person through respiratory secretions and typically sweeps through large groups of people who spend time in close contact.

Flu is spread when you inhale droplets in the air that contain the flu virus, make direct contact with respiratory secretions through sharing drinks or utensils, or handle items contaminated by an infected person. In the latter case, the flu virus on your skin infects you when you touch or rub your eyes, nose, or mouth. That's why frequent and thorough hand washing is a key way to limit the spread of influenza.

One of many examples of influenza outbreak,



InshaAllah, later I'll talk about surveillance and response system done by health sector to control the outbreak and preventing morbidity and mortality due to influenza outbreak.

References:

1. Student book block 4.2: Health System and Disaster

2. Emerging and Re-emerging Infectious Diseases, U. Desselberger, 2000

3. Epidemiology and pathogenesis of influenza, Maria C. Zambon, 1999

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