Clinical Update on Influenza
Dewi Dian Sukmawati
Division of Tropical and Infectious Disease Department of Internal Medicine
Udayana University School of Medicine-Sanglah Hospital Denpasar
Influenza ia a viral infection commonly attack upper respiratory tract; nose, throat, bronchi and occasionally spread to lungs. The viral spread easily from person to person via droplets and small particles produced by infected person when they cough or sneeze. The virus come from Orthomyxoviridae family, differentiated into three strain: Influenza virus A, B and C with most virulent strains belongs to the type A. The classification of Influenza virus A further based on the antigenic differences on their major surface antigens: Hemagglutinins (H1 – H5) and Neuraminidase (N1 – N9) Figure 1.
Figure 1. Influenza A virion
Some terms were use to describe the epidemiology of Influenza virus infection in human; seasonal influenza, pandemic influenza and zoonotic or variant influenza (Figure 2)
Seasonal influenza
Seasonal influenza viruses circulate and cause influenza in humans annually causing mild to severe illness and sometimes death, particularly in some high-risk individuals. Persons at increased risk for severe disease include pregnant women, infants and elderly, immune – compromised people, and people with co-morbidity chronic underlying medical conditions.
hemagglutinin or “H” protein and the neuraminidase or “N” protein. Currently, influenza A(H1N1) and A(H3N2) are the circulating seasonal influenza A virus subtypes. This seasonal A (H1N1) virus is the same virus that caused the 2009 swine influenza pandemic, as it is now circulating seasonally. In addition, there are two type B viruses that are also circulating as seasonal influenza viruses, which are named after the areas where they were first identified, Victoria lineage and Yamagata lineage. Type C influenza causes milder infections and is associated with sporadic cases and minor localized outbreaks. As influenza C poses much less of a disease burden than influenza A and B, only the latter two are included in seasonal influenza vaccines.
Pandemic Influenza
Pandemic influenza is a global outbreak. An influenza pandemic occurs when a new flu virus emerges for which humans have little or no immunity, which allows the virus to spread easily from person to person worldwide. These viruses may emerge, circulate and cause large outbreaks outside of the normal influenza season. As the majority of the population has no immunity to these viruses, the proportion of persons in a population getting infected may be quite large. Some pandemics may result in large numbers of severe infections while others will result in large numbers of milder infections, but the reasons behind these differences are not completely understood. Three influenza pandemics occurred during the 20th century: the 1918 – 1919 “Spanish flu,” the 1957 –
Figure 2. Influenza viruses in human
Influenza virus infections in humans. WHO 2014
Clinical Manifestations
The majority of person infected with influenza virus exhibit self limiting, uncomplicated, acute respiratory illness with fever or even asymptomatic (Figure 3).
The criterion standard for diagnosing influenza A and B is a viral culture of nasopharyngeal samples or throat samples. In elderly or high-risk patients with pulmonary symptoms, chest radiography should be performed to exclude pneumonia
Influenza Vaccine
Since the influenza seasons are unpredictable and influenza disease can have severe consequences, annual vaccination remains the best way to prevent the flu. Available vaccines including injectable and nasal spray form.
Seasonal Virus vaccine Trivalent types A and types B:
• Injectable vaccine
– Afluria. CSL Limited.
– Agriflu. Novartis Vaccines and Diagnostics, Inc.
– FluLaval. ID Biomedical Corporation of Quebec
– Fluarix. GlaxoSmithKline Biologicals
– Flublok. Protein Sciences Corporation
– Flucefax. Novartis Vaccines and Diagnostics, Inc.
– Fluvirin. Novartis Vaccines and Diagnostics Ltd.
– Fluzone, Fluzone highdose, Fluzone intradermal. Sanofi Pasteur, Inc.
• Intranasal spray
– FluMist. MedImmune, LLC
Seasonal Virus vaccine Quadrivalent types A and types B:
• Injectable vaccine
– Fluarix Quadrivalent. GlaxoSmithKline Biologicals
– Fluzone Quadrivalent. Sanofi Pasteur, Inc.
– FluLaval Quadrivalent. ID Biomedical Corporation of Quebec
• Intranasal spray
– FluMist Quadrivalent. MedImmune, LLC
Influenza virus vaccine for H5N1 (not available commercially, stock pile only used for outbreak):
• Influenza virus vaccine H5N1 Sanofi Pasteur, Inc
• Influenza A (H5N1) Virus Monovalent Vaccine Adjuvanted. ID Biomedical Corporation of Quebec
Antiviral Therapy
• Infected cases: Infected person will have milder sign and symptoms with shorter duration of illness. Antiviral medications work best when started within the first two days of flu onset.
• Exposed to the flu: antiviral medication can prevent Illness. But must be remember that antiviral drugs are not a substitute for the influenza vaccine.
Current approved antiviral for influenza including
• Tamiflu (oseltamivir phosphate)
• Relenza (zanamivir)
• Rapivab (peramivir)
Older drugs, such as amantadine and rimantadine possess resistance problem (including to H1N1 influenza) thus not widely be used anymore.
Refferences
1. Fiore AE, Shay DK, Broder K, et al. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2008. MMWR Recomm Rep 2008; 57(RR-7):1–60.
2. D’Heilly SJ, Janoff EN, Nichol P, Nichol KL. Rapid diagnosis of in- fluenza infection in older adults: influence on clinical care in a routine clinical setting. J Clin Virol Vaccines for preventing influenza in healthy adults. Cochrane Database Syst Rev. 2010 Jul 7. CD001269
