Statement from Institut Pasteur du Cambodge CAMBODIA A/H5N1 STRAIN DOES NOT CONTAIN MUTATIONS ASSOCIATED WITH HUMAN-TO-HUMAN TRANSMISSION
The Virology Unit at Institut Pasteur du Cambodge (IPC) serves at the National Influenza Center since 2007 and a WHO H5 Regional Reference Laboratory since 2013. On February 22nd, 2023, IPC received a sample for confirmation previously tested positive for A/H5N1 by the National Institute of Public Health. IPC confirmed the sample to be positive for A/H5N1 on the same day and was able to fully sequence the virus in less than 24 hours. After communication of all information to the Ministry of Health, the full genome virus sequence of was made available on GISAID on February 26th, 2023. IPC continues to work with Cambodian and international authorities surrounding this case, and no implications of human-to-human transmission have been found.
We would like to clarify recent statements in the press regarding the A/H5N1 virus detected recently in Cambodia that were taken out of context. The confusion surrounds the implication that the virus has already gone “through” humans. For clarification, The A/H5N1 virus isolated from the case in Cambodia shows certain changes that are anticipated and have been found in previous avian and/or human strains when they go from a bird to a human. This does NOT indicate that the virus is mutating or adapting to become human-to-human transmissible nor does it state that the virus has already transmitted between humans. Therefore, we would like to clarify the current state of scientific knowledge on the virus.
A/H5 viruses have caused infrequent spillovers into humans since emergence in 1997. There have been 870 reported human cases of A/H5 infection globally, resulting in 458 deaths. However, while avian influenza is a serious illness and any zoonotic transmission is concerning, it is rare in humans, and is typically linked to direct contact with infected birds or their droppings. No A/H5 avian influenza viruses have been demonstrated to have sustained human-to-human transmission.
The sequence of the Cambodian A/H5N1 virus, made freely available on GISAID, indicates the presence of mutations that occur naturally, and have been found previously in both avian viruses and/or other isolated human cases. The Cambodian A/H5N1 virus does NOT have the PB2 627 or hemagglutinin (HA) 225 changes experimentally associated with increased mammalian transmission. Any time a zoonotic virus gets into a new host, they can have certain changes that allow them small advantages to bind or replicate in that new host. These changes do not necessarily imply complete adaptation.
The presence of these changes does NOT imply the virus is fully human adapted or, in any way, becoming transmissible in humans. These naturally occurring mutations are a result of evolution and selective pressure on the avian influenza virus. The small adaptations have been detected in spillover events into humans in the past, and have not resulted in sustained human-to-human transmission. Rigorous experimental analysis is necessary to evaluate the effect of these mutations on this specific virus.
Any implication that this A/H5N1 virus is fully human adapted or transmissible between humans can lead to unwarranted fear among the general public about the risk of bird flu.
It is important that media outlets present accurate and balanced information to the public. We urge media organizations to take responsibility for the information they disseminate and to ensure that their reporting is based on sound scientific evidence and accurate quotation.
Director Office
Institut Pasteur du Cambodge
E-Mail : [email protected]