Swine flu is the common name for the novel influenza strain H1N1 that was first identified in the U.S. and Mexico in March 2009. According to the World Health Organization, swine flu is a pandemic with culture-proved cases reported in more than 200 countries and linked to more than 12,000 deaths, as of December 2009.
Clinical Diagnosis
According to the Centers for Disease Control and Prevention (CDC), most cases of swine flu are diagnosed "clinically," meaning on the basis of symptoms. Swine flu produces systemic, respiratory and gastrointestinal symptoms.
Systemic Symptoms
According to a 2009 article in the "New England Journal of Medicine," fever greater than 101.3 degrees F (38 degrees C) was the single-most common symptom of swine flu, present in more than 94 percent of cases. Other common systemic symptoms of swine flu include headache (61 percent) and joint or muscle pain (43 percent).
Respiratory Symptoms
According to a 2009 report in the "Journal of Clinical Microbiology and Infections," respiratory symptoms of swine flu, in decreasing order by prevalence, include cough (92 percent), sore throat (70 percent), runny nose (64 percent), nasal congestion (56 percent) and mild breathing problems (22 percent).
Gastrointestinal Symptoms
Seasonal flu is rarely associated with gastrointestinal symptoms. However, according to a report by the Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, almost 40 percent of swine flu patients reported vomiting, diarrhea or both.
Course
In most cases of uncomplicated swine flu, symptoms peak within a few days (two to three). Cough is usually the most persistent symptom, still present in more than 10 percent of patients 10 days after onset.
Diagnostic Tests
According to the CDC, rapid flu tests returns results within 30 minutes; however, they are designed for seasonal flu and miss between 70 and 90 percent of swine flu. Laboratory tests, such as polymerase chain reaction, are accurate, expensive and require several days to obtain results; they are often reserved for high-risk patients.
References
- Centers for Disease Control and Prevention: 2009 H1N1 Flu
- 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; November 13, 2009
