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Overnight the Chinese and Japanese press have been filled with numerous reports on a study led by Yoshihiro Kawaoka, DVM, PhD of the University of Tokyo
(and also the University of Wisconsin), on the transmissibility of H7N9 among ferrets via airborne droplets.
What isn't entirely clear is whether this is old information being rehashed by the press, or if a new study from Professor Kawaoka et al. is in the offing.
Reports include this English language broadcast from
NHK World (bolding mine):
Study: H7N9 bird flu transmittible via droplets
Japanese researchers say they have determined that the H7N9 avian influenza virus can be transmitted via respiratory droplets. It's the first time researchers have confirmed that a bird flu virus can be spread by airborne droplets.
The researchers say a new type of influenza comes about when a bird flu virus accumulates genetic mutations and becomes transmissible to humans.
(SNIP)
Professor Kawaoka warns that the H7N9 strain has the potential to cause a global pandemic.
And this from the
South China Morning Post:
Hong Kong to remain vigilant over bird flu threat, health chief Sophia Chan vows, as Japanese research confirms H7N9 virus can be transmitted via respiratory droplets
- University of Tokyo researchers find healthy ferret infected with virus after sick animal placed in separate cage 7cm away
I've looked at the
University of Tokyo website, and the usual research paper portals (
PubMed &
Google Scholar) this morning, and so far I've not found any new report on this topic, and none of the media reports I've seen link to a specific study.
Despite the `breaking news' tone employed by these media stories, as you'll see, this isn't exactly the first time we've heard about droplet transmission of the avian H7N9 virus in ferrets.
Just over a year ago, in
Cell Host & Microbe: HPAI H7N9 Lethality & Transmission In Ferrets, we looked at a study led by Dr. Kawaoka presenting very much similar results. A press release from the
University of Wisconsin-Madison stated:
H7N9 influenza is both lethal and transmissible in animal model for flu
University of Wisconsin-Madison
(Excerpt)
For the first time, Kawaoka says, his team has identified an influenza virus strain that is both transmissible between ferrets (the best animal model proxy for human influenza infections) and lethal, both in the animal originally infected and in otherwise healthy ferrets in close contact with these infected animals.
"This is the first case of a highly pathogenic avian virus that transmits between ferrets and kills them," Kawaoka says. "That's not good for public health."
(Continue . . . .)
And
the 2017 Cell Host & Microbe study featured these highlights:
Highlights
- Highly pathogenic avian influenza (HPAI) H7N9 viruses replicate efficiently in mammals
- HPAI H7N9 viruses are more pathogenic than low pathogenic H7N9 viruses in mammals
- HPAI H7N9 viruses transmit via respiratory droplets among ferrets
- HPAI H7N9 viruses show low sensitivity to neuraminidase inhibitors in mice
And we can go back even further, to the summer of
2013, where in
Nature: Limited Airborne Transmission Of H7N9 Between Ferrets researchers from the
Erasmus Medical Center in the Netherlands
& the
University of Cambridge in the United Kingdom infected four ferrets with
the Anhui/1/2013 strain of H7N9, and then place uninfected ferrets in
cages next to them.
Three of the four unexposed ferrets became infected, demonstrating limited airborne transmission (efficiency estimated somewhere between that of seasonal flu and avian flu). Genetic sequencing showed the virus they carried to be identical to the original test virus.
And the month before that, in
Science: H7N9 Transmissibility Study In Ferrets, a study by scientists from
Harbin Veterinary Research Institute and the
Gansu Agricultural University appearing in the
Journal Science offered a detailed look at two critical issues; the
pathogenicity and transmissibility of the virus
(in mice & ferrets).
This study tested several different H7N9 isolates (acquired from birds, and from humans) for transmissibility, and even though their HA and NA proteins were genetically quite similar, at least one H7N9 isolate transmitted readily via respiratory droplets among ferrets.
The abstract (
see below), only scratches the surface of research conducted in this study.
Science DOI: 10.1126/science.1240532
Qianyi
Zhang, Jianzhong Shi, Guohua Deng, Jing Guo, Xianying Zeng, Xijun He,
Huihui Kong, Chunyang Gu, Xuyong Li, Jinxiong Liu, Guojun Wang, Yan
Chen, Liling Liu, Libin Liang, Yuanyuan Li, Jun Fan, Jinliang Wang,
Wenhui Li, Lizheng Guan, Qimeng Li, Huanliang Yang, Pucheng Chen, Li
Jiang,Yuntao Guan, Xiaoguang Xin, Yongping Jiang, Guobin Tian, Xiurong
Wang, Chuanling Qiao, Chengjun Li, Zhigao Bu, Hualan Chen
Abstract (EXCERPT)
We
systematically analyzed H7N9 viruses isolated from birds and humans.
The viruses were genetically closely related and bound to human airway
receptors; some also maintained the ability to bind to avian airway
receptors. The viruses isolated from birds were nonpathogenic in
chickens, ducks, and mice; however, the viruses isolated from humans
caused up to 30% body weight loss in mice.
Most
importantly, one virus isolated from humans was highly transmissible in
ferrets by respiratory droplets. Our findings indicate nothing to
reduce the concern that these viruses can transmit between humans.
I'll keep an eye out for any new studies on this topic, but droplet transmission of H7N9 among ferrets -
while concerning - is not exactly breaking news.
Stay tuned.
