Question

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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 diagnosed 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 the ED with worsening cough, dyspnea, fever (101° F), and generalized lethargy. Additionally, she reported new symptoms including a global headache, dizziness, myalgia's, and arthralgia's. 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 hypertension, she smoked an average of a pack of cigarettes daily, and she 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, and azithromycin. Blood cultures drawn on her admission were negative, and an expectorated sputum sample taken at the 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. 1. What is the agent causing her infection? (explain with support). (1 point) 2. What are the key virulence factors of this agent? (explain with support) (1 point) 3. How does this virus change over time? What made this virus unique in 2009? (antigenic drift or antigenic shift) Explain the difference between the two types of mutations. (3 points) 4. What groups of people are at greater risk of a poor outcome when they are infected with the virus? (explain) (1 point) 5. What are the common complications associated with this infection that lead to increased morbidity and mortality? (explain) (2 points) 6. What antiviral drugs are available to treat this infection, and how do they work? Is there any concern for antiviral resistance? (2 points)

Answer 1

1.In accordance to the symptoms and patients poor prognosis the causative agent us H1N1 (Swine flu) virus causing influenza.

2.The virus enters the host by air,invades the respiratory tract ,affecting the linings of the respiratory tract.This causes impairment in the loss of function by decreasing the oxygen supply ,overtime causing fluid or air secretion and accumulation and causing extreme symptoms if not treated promptly the symptoms are irreversible and leads to death. The virulence of type B is more compared to type A virus.

3.Antigenic drift refers to accumulation of antigens from old virus and the antibody formed against this cannot recognise the new accumulated antigen of the same virus type and hence causing symptoms in patients

(If a patient is infected the body responds naturally by producing antibody against it and destroying it ,but this virus has a special character of having a very minute genetic variation each time they replicate (hence will have a new genetic character ) overtime when there is continuous accumulation of this new antigens ,the older antibody cannot destroy this making patients ill)

Antigenic shift refers to complete change of the genetic nature of each virus and making the diagnosis, treatment more complicated.

Type B belongs to antigenic drift and type A can be either antigenic drift or antigenic shift.

In 2009 the Type A virus (antigenic drift and antigenic shift) was pandemic

4.A people who are known case of diabetic,immunocompromised,children, elderly population, smoker,lung diseases are at a greater risk if poor outcome when they are infected with this virus.