# 7775
While we’ve heard very little regarding the H7N9 avian flu virus over the past four months, many experts worry that status could change as cooler temperature arrive this fall. So over the summer we’ve watched as a small parade of studies on this emerging virus have been published that have looked at everything from its susceptibility to antivirals, transmissibility in ferrets and mice, to its ability to bind to mammalian receptor cells.
Today, we’ve another study, this time looking at the effectiveness of common disinfection techniques in inactivating the H7N9 virus.
You may recall that 4 1/2 years ago, in Study: (H5N1): Effects Of Physico-Chemical Factors On Its Survival we looked at similar research done on the H5N1 virus. Should any pandemic virus begin to spread, the ability to disinfect hospital rooms, ambulances, medical equipment . . and yes - even sick rooms in private residences – becomes an important issue.
Today’s open access study appears in the Virology Journal, and may be viewed in its entirety at the link below:
Shumei Zou, Junfeng Guo, Rongbao Gao, Libo Dong, Jianfang Zhou, Ye Zhang, Jie Dong, Hong Bo, Kun Qin and Yuelong Shu
Virology Journal 2013, 10:289 doi:10.1186/1743-422X-10-289
Published: 15 September 2013
ABSTACT (Excerpts)Methods
To determine the inactivation effectiveness of the novel avian influenza A (H7N9) virus under various physical conditions and chemical treatments, two H7N9 viruses A/Anhui/1/2013 and A/Shanghai/1/2013 were treated by varied temperatures, ultraviolet light, varied pHs and different disinfectants. The viruses with107.7 EID50 were exposed to physical conditions (temperature, ultraviolet light and pH) or treated with commercial chemical agents (Sodium Hypochlorite, Virkon(R)-S, and Ethanol) respectively. After these treatments, the viruses were inoculated in SPF embryonated chicken eggs, the allantoic fluid was collected after 72--96 hours culture at 35[degree sign]C and tested by haemagglutination assay.
Results
Both of the tested viruses could tolerate conditions under 56[degree sign]C for 15 minutes or 60[degree sign]C for 5 minutes, but their infectivity was completely lost under 56[degree sign]C for 30 minutes, 65[degree sign]C for 10 minutes, 70[degree sign]C,75[degree sign]C and 100[degree sign]C for 1 minute. It was also observed that the H7N9 viruses lost their infectivity totally after exposure of ultraviolet light irradiation for 30 minutes or longer time. Additionally, the viruses were completely inactivated at pH less than 2 for 0.5 hour or pH 3 for 24 hours, however, viruses remained infectious under pH treatment of 4--12 for 24 hours. The viruses were totally disinfected when treated with Sodium Hypochlorite, Virkon(R)-S and Ethanol at recommended concentrations after only 5minutes.
Conclusions
The novel avian influenza A (H7N9) virus can be inactivated under some physical conditions or with chemical treatments, but they present high tolerance to moderately acidic or higher alkali conditions. The results provided the essential information for public health intervention of novel H7N9 avian influenza outbreak.
Like it’s H5 avian cousin, H7N9 is susceptible to heat (70C > 1 min), prolonged UV exposure (30 mins), strong acids and alkalis, and the usual disinfectants like bleach (Sodium Hypochlorite), alcohol (75%), and Virkon ®-S when applied at their recommended concentrations and for the recommended length of time (usually 5 minutes).
H7N9 appears unusually tolerant of moderate acids and alkalis', maintaining its infectivity under pH 4–12 conditions for 24 hours, or under pH 3 conditions for 30 minutes. To illustrate of the relative acidity and alkalinity of various common substances, I’ve reproduced the following chart from Wikipedia.
By comparison, the 2009 study (Avian influenza virus (H5N1); effects of physico-chemical factors on its survival) found the H5N1 subtype was a less tolerant of its environmental pH – losing its viability when exposed to pH 1, 3, 11 and 13 after 6 hours, and was inactivated at pH 5 after 24 hours.
I’ve reproduced today’s study conclusion below:
The results indicated that the novel avian influenza H7N9 viruses can be completely inactivated using high temperature (e.g. 56°C or above),UV light irradiation,and commercial disinfectants (Sodium Hypochlorite, Virkon®-S and Ethanol). But the virus presents a high tolerance to moderately acidic or higher alkali conditions. The present results would provide essential information for public health intervention of novel avian influenza H7N9 outbreaks.
Perhaps the biggest takeaway message here is that while disinfection of surfaces using standard techniques will work, attention must be paid to disinfectant concentrations and to (disinfectant, heat, UV) exposure times. Tasks that housecleaning personnel in hospitals are quite familiar with.
On the other hand, the kind of cursory cleaning one might do in one’s home, or that might be done by a cleaning staff at a motel, hotel, restaurant, or at work (ie. giving a surface a quick wipe down with a household cleaner/disinfectant) might not be sufficient to kill the virus.
Something to consider during every cold & flu season, not just when a novel virus threatens.
And an excellent reason to remember to practice good flu hygiene (frequent hand washing/sanitizing, avoid touching your face, covering coughs & sneezes, and staying home if you are sick) all year round.
