What is H5N1?
H5N1 (bird flu) is one of several influenza viruses that causes highly infectious respiratory disease in birds, also known as avian influenza. It is an influenza A virus, and among birds, it is highly contagious. While it’s typically rare for H5N1 to infect anything other than birds, there have recently been large outbreaks of H5N1 in dairy cattle, and several human cases. Human infections in the US have mostly occurred among people who work closely with poultry or cattle, and thankfully most recent human infections have had mild symptoms. To date, no human-to-human transmission of H5N1 has been documented. The increase in human infections is concerning because H5N1 has historically had a high fatality rate in humans. Because influenza viruses mutate frequently, there is also concern that H5N1 could develop mutations that enable it to spread more easily among humans, posing a pandemic risk. There are large efforts underway to prevent further spread of H5N1 among humans, including efforts by USDA, FDA, and CDC.
How is it different from seasonal flu?
Seasonal flu, which circulates annually in humans in the US, is usually caused by four main influenza viruses: two influenza A subtypes (H1N1 and H3N2) and two influenza B lineages (Victoria and Yamagata). These subtypes are well-adapted to humans and are the most common causes of flu each year. Most human infections are caused by H1N1 or H3N2. Bird flu (H5N1) can infect humans through close contact with infected birds, cattle, or contaminated environments, but it is not spread easily from person to person. Bird flu is not responsible for seasonal flu cases in humans.
How do you detect H5N1? What assay do you use?
The assay, H5* influenza, was designed with primers and probes to detect H5N1 subtypes from avian, cattle, and human origin by digital droplet PCR.
Can I compare my H5N1 data to Influenza A data?
Not easily. Although H5N1 does contribute to the total influenza A concentration in a sample, the H5* influenza and influenza A assays target different genes that make data comparison between the two targets more challenging than using a simple ratio. This is why sometimes the H5N1 concentration will appear to be larger than the influenza A concentration of the same sample.
What is the sensitivity of your assay?
The analytical sensitivity of the assay is about 0.73 copies per mL. Though the assay was designed for the detection of the H5N1 subtype, the assay has also been demonstrated to detect influenza subtypes H5N6 and H5N9. These subtypes also cause avian influenza. H5N6 has infected humans rarely, but H5N9 is not yet known to infect human hosts.The assay is not expected to detect H3, H1, or influenza B subtypes.
Can your assay detect different genotypes of H5N1 (for example the genotype spreading in birds versus cattle?)
The assay is comprehensive such that different genotypes will be included in the H5N1 data, however the assay cannot differentiate between the genotypes.
Can your assay tell the difference between H5N1 that has infected humans vs other animals? Or if it’s coming from milk?
No, the assay cannot provide insight on the origin of the virus.
Can you detect other subtypes of influenza?
Yes, besides the H5* assay, we also offer testing and data delivery for H3, H1, influenza A, influenza B, as well as influenza B sublineages B-Yam and B-Vic.