[A pathogenic and clinical study of 882 cases of adult influenza-like illness in Guangzhou].

OBJECTIVE

This study was undertaken to describe the viral etiology and clinical features in patients with influenza-like illness (ILI) in Guangzhou.

METHODS

The nasopharyngeal and throat swabs were collected from 882 patients presenting with ILI between January and September, 2009. Viral pathogens were cultured and identified by immunofluorescence technique using the Shell-Vial method. The clinical data were statistically analyzed.

RESULTS

(1) Viral etiology. Of the 882 samples, 385 (43.7%) were confirmed to have at least one of the 9 different respiratory viruses detected. Among these viral isolates, 67.3% (259/385) were seasonal influenza A virus, 27.8% (107/385) were influenza B virus, and 1.3% (5/385) were human parainfluenza virus (PHIV) 1, 2, or 3. In addition, 2 cases (0.5%) of each adenovirus, HSV-1, enterovirus and respiratory syncytial virus (RSV) were also found in the samples. Co-infections with more than one virus were revealed in 8 (2.1%) of 385 samples tested, among them 6 samples were mixture of influenza A and influenza B, 1 sample was positive for both influenza B virus and HPIV-3, and 1 was for both adenovirus and RSV. Seasonal influenza B virus appeared endemic between March and May, and seasonal influenza A virus became dominant between June and August. (2) Clinical features. The percentage of patients aged from 18-30 years was much higher than that of other age groups. The most common symptoms were moderate fever and sore throat, followed by cough. The percentage of upper respiratory infection and pneumonia was 88.4% (727/882) and 10.7% (95/882) respectively. Clinical features did not discriminate between patients with seasonal influenza A and those with influenza B virus infection. The average numbers of leukocytes and lymphocytes were lower in the group positive for influenza viruses than in virus negative group. The patients with adenovirus, HPIV and RSV infection were significantly younger. No rash was observed in patients with enterovirus or HSV infection.

CONCLUSIONS

(1) Seasonal influenza virus was the major viral etiologic agent of ILI in Guangzhou during the first 9 months in 2009. Influenza B and A viruses seasonally prevailed in spring and summer, respectively, while other viral etiologic agents appeared to be sporadic. (2) The analysis of clinical features in patients with ILI indicated that fever was the most common symptom, with body temperature varying greatly, and may be associated with evident respiratory and occasionally systemic symptoms. Among the cases with viral infection, the upper respiratory presentation was universal, and pneumonia was frequently noticed.