The presence of nipah virus in respiratory secretions and urine of patients during an outbreak of nipah virus encephalitis in Malaysia

Objectives: To study the excretion of Nipah virus in the upper respiratory secretions and urine of infected patients in relation to other clinical features. Methods: Isolation of Nipah virus from the respiratory secretions and urine was made in Vero cells and identified by indirect immunofluorescence assay using anti-Hendra specific hyperimmune mouse ascitic fluid and FITC-conjugated goat anti-mouse IgG. Results: During the peak outbreak of Nipah virus encephalitis in Malaysia, Nipah virus was isolated from the upper respiratory secretions and urine in eight of 20 patients who were virologically and/or serologically confirmed to be infected with the virus. From these eight patients, Nipah virus was isolated from six throat swab specimens, three urine specimens and only one nasal swab specimen. The positive virus isolation rate was related to the collection of these specimens during the early phase of the illness (P=0.068). The presence of serum anti-Nipah specific IgM appeared to reduce the chance of isolating the virus (P=0.049). There was no significant difference in the isolation rate with respect to the age, gender, ethnic group and clinical features associated with grave prognosis and mortality outcome of the patients. Conclusion: This study shows that it is possible to be infected from secretions of infected patients, but epidemiological survey on close contacts so far did not suggest that human-to-human transmission is common.