Swine flu is the common name of the novel strain of influenza A now known as H1N1. According to a May 2009 article in "Lancet," the interval between exposure to swine flu and the appearance of symptoms averages 1.4 days. However, not all symptoms appear at the same time; the incubation period for specific symptoms of swine flu varies.
Systemic Symptoms
Systemic symptoms of swine flu are markers that the infection has spread throughout the body and include fever, headache and muscle pain. According to a 2009 report by the Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team, fever is the single most common symptom of swine flu, present in 94 percent of patients. Fever is usually the first symptom of swine flu; however, some adults report that muscle pain preceded fever by one or two days.
Respiratory Symptoms
Swine flu is associated with both lower respiratory symptoms like cough and breathing problems and upper respiratory symptoms like sore throat, runny nose and nasal congestion. According to a 2009 article in the "Journal of Clinical Microbiology and Infections," cough is the second most common symptom of swine flu, appearing in 92 percent of patients. Cough may appear one or two days before fever or at the same time. Upper respiratory symptoms usually appeared somewhat later in the course of illness.
Gastrointestinal Symptoms
A distinguishing feature of swine flu compared to seasonal flu is the presence of gastrointestinal symptoms such as diarrhea and vomiting. According to a 2009 article in the "New England Journal of Medicine," about 40 percent of patients complained of one or both symptoms. These symptoms usually appeared one to two days after the onset of fever.
References
- Lancet Infectious Disease; Incubation Periods of Acute Respiratory Viral Infections: A Systematic Review. J Lessler, NG Reich, R Brookmeyer, TM Perl, KE Nelson, DA Cummings; May 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); CS Lee, H Lee; November 13 2009
