Doctors have seen what they believe is the first case of person-to-person transmission of a new strain of bird flu in Eastern China, with the polymerase chain reaction (PCR) providing the evidence. The report, which provides the strongest evidence of transfer of the H7N9 avian influenza A virus between two people to date, was published in the BMJ.
The H7N9 strain, which has not been reported in humans before, has led to 133 reported cases (as of 30 June 2013), with 43 deaths. Most cases have been linked with visits to live poultry markets or close contact with live poultry.
The first patient, a 60-year-old man, visited a live poultry market and became ill five or six days after his contact with live poultry, and was admitted into hospital on 11 March 2013. He was moved to the intensive care unit on 15 March, transferred to another ICU on 18 March, and died on 4 May. His 32-year-old daughter had no known exposure to live poultry but provided unprotected care for her father at home and in hospital before he was admitted to the ICU. She developed symptoms six days after her last contact with her father, and was admitted into hospital on 24 March. She was moved to the ICU on 28 March and died on 28 April.
Samples from the father and daughter were tested using real time reverse transcriptase PCR (rRT-PCR), along with viral culture and haemagglutination inhibition assay. This confirmed that both carried almost genetically identical viral strains. Their close contacts (43 in total, including family, friends and healthcare workers) were tested, including the son-in-law who also cared for the father and who became mildly ill, but none was carrying the H7N9 infection. Tests of the poultry cages, bird faeces and water at the local markets, and swabs from local wild swans birds, were also carried out using rRT-PCR and other assays, and showed no evidence of the same strain.
These results suggest that the virus transmitted directly from father to daughter. The researchers describe the virus’s ability to transmit itself from human to human as “limited and non-sustainable as there is no outbreak following the two cases”, and that “the virus has not gained the ability to transmit itself sustained from person to person efficiently.”
While this virus is unlikely to become pandemic, and the researchers admitted weaknesses in the study, including not being able to rule out that the daughter caught the virus elsewhere, the findings from this isolated incident could teach scientists more about how the virus adapts, and provide routes to treatments and vaccines. As the father and daughter both carried the virus but others did not, it could suggest a genetic susceptibility to infection, which may prove significant in prophylaxis and treatment. It also reinforces the need to remain vigilant against new viruses.
The study also reinforces the strength of PCR in virological research as well as diagnosis, and the importance of fast turnaround in PCR analysis in the face of new strains of virus.
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Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.