(HealthDay News) — Most infection cases from the H7N9 virus in China are epidemiologically unrelated, although limited human-to-human transmission cannot be ruled out, according to a study published in the February 6 issue of the New England Journal of Medicine.

Qun Li, MD, from the Chinese Center for Disease Control and Prevention in Beijing, and colleagues conducted field investigations for each confirmed case of H7N9 virus infection (139 patients; mean age 61 years). Confirmed cases were verified by real-time reverse-transcriptase-polymerase-chain reaction assay, viral isolation, or serologic testing. Throat swabs were taken and tested from contacts who showed symptoms during seven days of monitoring.

The researchers found that, of the confirmed cases, 71% were male and 73% were urban residents, and nine people were poultry workers. Twelve areas had confirmed cases. For the 131 persons with available data, 82% had a history of exposure to live animals, including chickens (82%). Nearly all (99%) were hospitalized, with 63% (65 of 103 with available data) admitted to an intensive care unit. The majority of hospitalized patients (125 of 137) had pneumonia or respiratory failure. Just over one-third (47) died in the hospital after a median duration of illness of 21 days, while 88 patients were discharged from the hospital. Human-to-human transmission of H7N9 virus could not be ruled out in four family clusters.

“Most persons with confirmed H7N9 virus infection had severe lower respiratory tract illness, were epidemiologically unrelated, and had a history of recent exposure to poultry,” the authors write. “However, limited, nonsustained human-to-human H7N9 virus transmission could not be ruled out in four families.”

Full Text (subscription or payment may be required)