CASE In December 2009, a 45-year-old female presented to the emergency departmen

Question

CASE In December 2009, a 45-year-old female presented to the emergency department (ED) 2 days following abrupt onset of sore throat, nonproductive cough, chills, and mild fever. A chest radiograph was performed, which was normal. She was diag nosed with bronchitis and asked to follow up with her primary care physician, who subsequently started her on levofloxacin and albuterol. Four days later she presented again to the ED with worsening cough, dyspnea, fever (38.3°C; 101°F), and generalized lethargy. Additionally, she reported new symp- toms including a global headache, dizziness, myalgias, and arthralgias. She had no abdominal pain, but reported nausea and anorexia. Her chest radiograph showed diffuse reticulonodular opacities throughout the left lung, which were not present on her visit 4 days previously. The patient was admitted for further evaluation. Questioning revealed the following: she had a history of diabetes and hyperten- sion, she smoked an average of a pack of cigarettes daily, and she had received the seasonal influenza vaccine. Her husband was recently ill with cough, but no other symptoms. On day 2 of hospitalization the patient's respiratory rate increased from 22 to 46 and her oxygen saturation dropped while on oxygen administered by nasal cannula. She was transferred to an intensive care unit, where her respiratory status quickly deteriorated, necessitating emergency intubation. A new chest radiograph showed bilateral involvement, and she was begun on vancomycin, aztreonam, an azithromycin. Blood cultures drawn on her admission were negative, and an expectorated sputum sample taken at the same time was not processed due to poor specimen quality. A PCR test performed on a nasopharyngeal swab was positive for a viral agent, revealing the etiology of her infection (Fig. 10.1) 1. What is the agent causing her infection? What are the key virulence factors of this agent? 2. How does this virus change over time? What made this virus unique in 2009?

Explanation / Answer

Question 1: The agent causing her infection is most probably influenza (H1N1) virus

Virulence factors: Human influenza virus can evolve rapidly by 2 mechanisms

Question 6: Antiviral drugs used for H1n1 infection

Oseltamivir - The neuraminidase inhibitor oseltamivir formulated as capsules or oral suspension is FDA-approved for the treatment of unsophisticated acute influenza in patients from 1 year and above who have not been symptomatic for more than 2 days.

Zanamivir - The neuraminidase inhibitor zanamivir formulated for oral inhalation is another FDA-approved for the treatment of influenza in patients 7 years of age and older who have unsophisticated acute infection and have been symptomatic for no more than 2 days.

Peramivir - A third neuraminidase inhibitor peramivir formulated for intravenous (IV) administration is an investigational product which is currently being evaluated in clinical trials.

Resistance: Oseltamivir resistance is common among seasonal influenza A (H1N1) viruses. However these viruses normally remain vulnerable to zanamivir, rimantadine, and amantadine.

M.O.A. – Neuraminidase inhibitors act as a transition-state analogue inhibitor of influenza neuraminidase. Which ultimately prevent emergence of new viruses from the infected cells.

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