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Introduction | The Virus | Strains | Antegenic Shift/Drift | Symptoms | H5N1 | Infection | Resevoirs of Infection | Conclusion
Symptoms of Influenza in Humans
a) Common Symptoms
Symptoms of Influenza in Humans |
Fever (above 40 ° C) |
Chills (possibly with shivering) |
Muscle aches and pains |
Sweating |
Sore Throat |
Nasal Congestion |
Dry Cough |
Headache |
Fatigue |
Malaise |
b) Signs and Risks
Although the virus is deposited in the respiratory tract, signs and symptoms can be observed and detected throughout the entire body. Contrary to common belief, Influenza is actually pathologically distinct from diseases like the common cold or the stomach flu. Both stated diseases are often confused with the “flu”, which is incorrect. The range of severity of the symptoms of flu is wide and can be mild rhinitis at one end, to even fatal pneumonia at the other.
Some common signs and symptoms of flu are:
Abrupt onset of symptoms
Patients may have the feeling of being completely pin down during the initial hours of rapidly appearing symptoms. This happens within about 2 to 4 days of incubation. Cold symptoms instead appear over a course of a few days. |
Fever
Patients usually experience a fever of over 37.8 ° C on the first day. This would usually subside on the second to third day. However, in more serious patients, fever may spike again on the third or fourth day. |
Chills / Sweats / Headache
Patients may (or may not) develop chills, headaches and/or sweating before or accompanying the fever. |
Sore Throat
Sore throat experiences usually described as a “burning” sensation. |
Dry Cough
Happens at the onset of illness. |
Substernal soreness, photophobia and ocular problems
When severe substernal pain is detected, it usually point towards the primary involvement of the trachea. Other symptoms also include prolonged fatigue, weakness and general distresses like diarrhoea and nausea. |
Malaise
Severe and persistent Malaise. |
Myalgia
Possible severe myalgia will occur, usually in the back and the extremities. Related to the severity of the fever. |
When symptoms first appear, constitutional symptoms would seem more severe then respiratory symptoms. However, when the former subsides, respiratory symptoms become more evident.
Typical signs and symptoms of flu in adults include an abrupt onset of symptoms within 2 to 4 days of incubation of the virus. These symptoms include fever which surpasses 37.8 ° C that peaks within the first day. This will continue on for about another 4 days. Other symptoms include dry cough, headaches, chills, sweating, sore throat, myalgia, malaise and anorexia. One key differentiating factor of influenza infection from other common respiratory illnesses is that symptoms of malaise would severe and persists for several days. Other symptoms may include muscle fatigue, photophobia and other general distresses like abdominal pains and nausea. As for children, they experience relatively the same type of symptoms except that abdominal distress and myalgia appear more frequently. Their maximum temperature may also be higher, indicating febrile convulsions. Symptoms such as headaches and malaise are usually difficult for children to verbalize and express and may have occurred earlier than they first appeared. Fever and rhinitis are common in children of ages less than 5. In very young infants, rhinitis might be the only respiratory symptom.
In comparison to adults or teenagers, patients in the lower age groups usually tend to experience more of vomiting or diarrhoea. These symptoms nevertheless can be easily detected. However, symptoms such as malaise or myalgia are more difficult to identify in children if present.
c) Flu vs Cold Symptoms
Signs and Symptoms |
Flu |
Cold |
Onset |
Sudden |
Gradual |
Fever |
High (over 38° C), usually lasting 3 to 4 days |
Rare |
Nasal Congestion |
Sometimes |
Usual |
Sneezing |
Sometimes |
Usual |
Dry Cough |
Non-productive and can become severe |
Hacking |
Sore Throat |
Sometimes |
Common |
Headache |
Prominent |
Rare |
Myalgia (aches and pains) |
Usual, often severe |
Slight |
Fatigue and weakness |
May last for 2, 3 weeks |
Very mild |
Extreme exhaustion |
Early and prominent |
Never occurs |
Chest discomfort |
Common |
Mild |
d) Reported Symptoms Of Avian Influenza
Reported symptoms of Avian Influenza in human subjects ranged from typical influenza symptoms as mentioned above, to eye infections (conjunctivitis), severe pneumonia and respiratory diseases such as viral pneumonia, acute respiratory disorder and other possibly fatal complications. The symptoms of Avian Influenza depend on what type of virus caused the infection. |