Upper Respiratory Tract Infections - Influenza

Influenza
Influenza is a specific acute viral respiratory disease characterized by fever, coryza, cough, headache, and malaise, and inflamed respiratory mucous membranes. It usually occurs as an epidemic in rainy seasons.

Etiology: It is caused by influenza viruses, which are classified as orthomyxovirus. There are types A, B & C

Epidemiology:

• Influenza type A virus is the most frequent single cause of clinical influenza; other causes include influenza B, paramyxovirus, pneumonia-virus, and (rarely in adults) rhino and echoviruses.

• Spread is by person - to - person contact; airborne droplets spray infects people and contaminates articles with viruses that can transmit infection.

• Persons of all ages are affected, but prevalence is highest in school children.

• Persons at highest risk of developing severe disease are those with chronic pulmonary disease and those with valvular heart disease, pregnant women, the elderly, the very young and the bed ridden.

• Infection with influenza A is associated with significant morbidity and mortality.

Symptoms and Signs:
• During the 48-hour incubation period, transient asymptomatic viremia occurs.

• Then there is chills and fever up to 39 to 39.5 0c developing over 24 hr.

• Generalized aches and pains (most pronounced in the back and legs) appear early.

• Headache is prominent.

• Respiratory tract symptoms may be mild initially but become prominent later.

• The soft palate, posterior hard palate, and tonsillar pillars may be reddened. Usually, after 2 to 3 days, acute symptoms rapidly subside and fever ends.

• Weakness, sweating and fatigue may persist for several days or occasionally for weeks.

• In severe cases, hemorrhagic bronchitis and pneumonia are frequent and can develop within hours.

• Fulminant, fatal viral pneumonia may occur and death may follow as soon as 48 hr after onset. This is usually during a pandemic caused by a new virus or in high-risk people.

Complication:

• Secondary bacterial infection of the bronchus and pneumonia. With pneumonia, the cough worsens and purulent or bloody sputum is produced. Crepitations can be detected over the affected segment.

• Encephalitis, myocarditis, and myoglobinuria may occur as complications of influenza, usually during convalescence.

Diagnosis:

• Clinical influenza is a common experience and can easily diagnosed. Chest examination is usually normal in mild cases and may look like common cold. Pulmonary symptoms may be similar to those of bronchitis or atypical pneumonia. Fever and severe constitutional symptoms differentiate influenza from the common cold

• The leukocyte count is normal in uncomplicated cases.

• Isolating the virus can make specific diagnosis of influenza. Serologic tests are also used.

Prognosis: Recovery is the rule in uncomplicated influenza. Viral pneumonia may cause death.

Prophylaxis: Vaccines that include the prevalent strains of influenza viruses effectively reduce the incidence of infection. Amantadine 100mg orally bid (for adults) can be used prophylactically against influenza A.

Treatment:

• Amantadine has a beneficial effect on fever and respiratory symptoms if given early in uncomplicated influenza.


• Basic treatment for most patients is symptomatic with bed rest, antipyretics, nasal decongestants & steam inhalation.

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