Researchers Report Probable Person-to-Person Transmission of H7N9

Qi, et al. (2013) sought to determine whether the novel avian influenza H7N9 virus can transmit from person to person and its efficiency. The researchers conducted epidemiological investigations after a family cluster of two patients with avian H7N9 was discovered in March 2013 in Wuxi, Eastern China.

Samples from the patients and environments were collected and tested by real time reverse transcriptase-polymerase chain reaction (rRT-PCR), viral culture, and haemagglutination inhibition assay. Any close contacts who became ill had samples tested for avian H7N9 by rRT-PCR. Paired serum samples were obtained from contacts for serological testing by haemagglutination inhibition assays.

The index patient became ill five to six days after his last exposure to poultry. The second patient, his 32-year-old daughter who provided unprotected bedside care in the hospital, had no known exposure to poultry. She developed symptoms six days after her last contact with her father. Two strains were isolated successfully from the two patients. Genome sequence and analyses of phylogenetic trees showed that both viruses were almost genetically identical. Forty three close contacts of both patients were identified. One had mild illness but had negative results for avian H7N9 by rRT-PCR. All 43 close contacts tested negative for haemagglutination inhibition antibodies specific for avian H7N9.

The researchers say the infection of the daughter probably resulted from contact with her father (the index patient) during unprotected exposure, suggesting that in this cluster the virus was able to transmit from person to person. The transmissibility was limited and non-sustainable. Their research was published in BMJ.

Reference: Qi X,  Qian YH, et al. Probable person to person transmission of novel avian influenza A (H7N9) virus in Eastern China, 2013: epidemiological investigation. BMJ 2013. 347:f4752.