Swine influenza is the common name for the influenza A (H1N1) virus. According to the World Health Organization (WHO), it is a new virus strain that can affect humans. In comparison to seasonal influenza, WHO warns that swine influenza is spreading particularly quickly among younger people aged 10 to 45. Like seasonal influenza, swine influenza mainly affects the immune system, the respiratory tract and the gastrointestinal tract.
Immune System Effects
Systemic effects of swine influenza reflect the response of the immune system to the infection. Common systemic effects include fever, headache, and muscle or joint pain. According to a 2009 report in the "New England Journal of Medicine," fever greater than 101.3 degrees F (38 degrees C) is the single most common effect of the swine influenza, present in 94 percent of laboratory-confirmed cases. In adults, the first effects of swine influenza may be headache or muscle/joint pain, followed a few days later by fever.
Respiratory Effects
The swine influenza affects both the upper and lower respiratory tracts. Lower respiratory effects include cough and breathing problems, reported in 92 and 22 percent of people, respectively, according to a 2009 study published in the "Journal of Clinical Microbiology and Infections." Upper respiratory tract effects include sore throat (64 percent of people), runny nose (56 percent) and nasal congestion (43 percent). According to the findings of the Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, cough may precede fever by one or two days, or begin around the same time. Upper respiratory tract effects tend to appear after lower respiratory tract effects, and are usually mild. Cough is often the most persistent effect of the swine influenza, lasting longer than 10 days in about 10 percent of infected people.
Gastrointestinal Effects
In contrast to seasonal influenza, the swine influenza frequently affects the gastrointestinal tract. According to the Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, vomiting, diarrhea or both were reported by almost 40 percent of outpatients with a laboratory-confirmed swine virus. These effects may be more pronounced in severe cases, requiring hospitalization. In most cases, vomiting and diarrhea were mild, and appeared a few days after fever and cough.
References
- WHO: What Is Pandemic H1N1 2009?
- "New England Journal of Medicine"; Emergence of a Novel Swine-Origin Influenza A (H1N1) Virus in Humans; Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team; June 18, 2009
- "Clinical Microbiology and Infections"; Dynamics of Clinical Symptoms in a Case with Pandemic Influenza A (H1N1); C.S. Lee and J.H. Lee; Nov. 13, 2009
