Study: (H5N1): Effects Of Physico-Chemical Factors On Its Survival

 

 

# 2949

 

 

Actually, the full name of the study which just appeared in the Virology Journal is:

 

Avian influenza virus (H5N1); effects of physico-chemical factors on its survival

Muhammad Akbar Shahid, Muhammad Abubakar1, Sajid Hameed2 and Shamsul Hassan

 

And before you turn away, this study is actually more interesting than it sounds.

 

The authors wanted to find out how long, and under what conditions, the H5N1 virus can survive intact in the environment, and the best ways to kill it.    

 

Answers to which are of interest to just about all of us.

 

Even if the virus never obtains pandemic capability, it still remains an environmental hazard (to poultry, and to people) in areas where it has become endemic.  

 

Right now, that includes countries like Egypt, Indonesia, China, India, Pakistan, and Vietnam . . . but someday it could also include the United States, Canada, and Europe.  

 

And the threat isn’t limited to just the H5 viruses, there are H7 and H9 viruses in circulation that are of concern as well.

 

Vaccination of poultry is considered, at best, to be a stopgap measure.  Eradication of infected birds and the disinfecting of contaminated environments is the preferred method of control.

 

Researchers in Pakistan isolated the H5N1 virus during an outbreak in 2006 and cultivated it in embryonated chicken eggs. 

 

They then harvested the allanto-amniotic (AAF) fluid containing the virus, and used it in a variety of environmental and chemical tests to see how long the virus remained viable.

 

The results are illuminating.

 

Some excerpts from the study follow, with the first regarding viability at various temperatures, and the effects of UV light:

 

Avian influenza virus H5N1 retained its infectivity at 4°C for more than 100 days although HA activity was decreased.

 

Virus lost its infectivity after 24 h  when kept at room temperature (28°C).

 

Virus tolerated 15 min exposure to 56°C however it was inactivated at 56°C after 30 min of exposure.

 

Ultraviolet light had no deleterious effect on the virus replicating ability even after 60 minutes of exposure (Table 1).

 

 

Virus samples were exposed to Acid (pH < 7) and Basic  (pH > 7) solutions to determine at what level of acidity or alkalinity were viruses inactivated.

 

 

It was observed that H5N1 subtype lost its viability when exposed to pH 1, 3, 11 and 13 after 6 h while it remained viable at pH 7 for all contact times (6, 12, 18 and 24 h).

 

It retained its virulence at pH 5 for 18 h but got inactivated after 24 h.

 

Virus retained its infectivity at pH 9 for more than 24 h (Table 2).

 

To give the lay person some idea of the relative acidity and alkalinity of various common substances, I’ve reproduced a chart from the Wikipedia.

 

 

 

The prolonged contact time required to inactivate the virus even at relatively high and low pH levels tends to makes their use problematic to control the virus.

 

With regards to commonly used disinfecting agents in laboratories and hospitals, better results were achieved:

 

 

H5N1 was inactivated with formalin (0.2, 0.4 and 0.6% after 15 minutes)

 

Iodine crystals (0.4 and 0.6% after 15 minutes)

 

Phenol crystals (0.4 and 0.6% after 15 minutes)

 

CID 20 (0.5% after 60 minutes and 1.0% after 15 minutes)

Virkon®-S (0.2% after 45 minutes, 0.5 and 1.0% after 15 minutes)

 

Zeptin10% (0.5% after 45 minutes, 1% after 30 minutes and 2% after 15 minutes)

 

KEPCIDE300 (0.5% after 30 minutes and 1% after 15 minutes) and KEPCIDE 400 (0.5 and 1.0% after 15 minutes) at 28°C.

 

And finally, soap and detergents were tested:

 

Lifebuoy, Surf Excel and Caustic soda inactivated the virus at 0.1, 0.2 and 0.3% concentration after 5 minutes contact time while a concentration of 0.05% was not enough to kill virus (Table 4).

 

The authors make it clear that:  Each commercial preparation is the result of careful formulation and any modification can reduce the efficacy.

In other words, use according to directions!

 

While the virus is relatively easily inactivated by commonly used disinfecting methods, left unchallenged, at low temperatures and in a suitable medium, the virus can remain viable for days, weeks, or even months.

 

All of this, right now, is mostly of concern to those charged with maintaining bio-security measures at farms and hatcheries in the wake of avian influenza virus outbreaks, it could someday have broader implications.

 

This study is another step along the path of understanding how avian flu viruses survive (or not) in the environment, and how to eradicate them.