In April 2009, researchers at the Centers for Disease Control and Prevention (CDC) announced the discovery of a new flu strain now known as 2009 H1N1 or "swine flu." According to the CDC, the new flu strain contains genes from flu strains that commonly affect pigs in Asia and Europe as well as genes from strains that affect birds and humans. Symptoms of the new flu strain are very similar to symptoms of seasonal flu, although there are some differences.
Fever
In a June 18, 2009, report in the "New England Journal of Medicine," members of the Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team reported that the single most common symptom of swine flu was fever. According to the report, 94 percent of adults and children with swine flu complained of fever. In most cases, according to "Harrison's Principles of Internal Medicine," fever ranges from 100.4 to 105.8 degrees F. However, the absence of fever doesn't necessarily exclude a diagnosis of flu; some people are unable to mount a fever in response to illness.
Cough
According to the same report in the "New England Journal of Medicine," cough was the second most common symptom of the new flu strain, present in 92 percent of cases. Although cough presents first, many people develop other respiratory symptoms a few days later. In a 2009 article in the "Journal of Clinical Microbiology and Infections," researchers reported that 70 percent of patients also complained of other symptoms including sore throat, runny nose, nasal stuffiness and difficulty breathing.
Vomiting and Diarrhea
An unusual characteristic of the new flu strain compared to earlier strains is the frequency of gastrointestinal symptoms. According to the CDC, seasonal flu in adults is rarely associated with gastrointestinal symptoms; children may be somewhat different. However, with the new flu strain, researchers in the "Journal of Clinical Microbiology and Infections" reported that 40 percent of patients suffered from vomiting, diarrhea or both. In almost all cases, gastrointestinal symptoms started after and ended before other kinds of symptoms.
References
- CDC: 2009 H1N1 Flu ("Swine Flu") and You
- "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 and JH Lee; Nov. 13 2009
