H5N1 Avian Influenza History And Disease Characteristics
As a rule, influenza viruses seem to be very specific in terms of which species is affected by which virus strain. This means that a virus that is infecting birds, pigs, horses or even seals, will generally continue to only infect those specific species. Rarely will a virus “leak “into a different species. In the last fifty years cases of human contagion due to an avian influenza have been recorded in only ten instances. There are literally hundreds of varieties of avian influenza virus and yet just four have been confirmed as having caused any human infection: H5N1, H7N3, H7N7, and H9N2. When these viruses infected humans the result was only mild sickness and light symptoms – exceedingly slight harsh illness and only one is the exception, the extremely transmittable H5N1 bird virus.
There are many flu viruses in the avian populations but the H5N1 infection is the most worrisome for health service officials for a couple reasons.
One, H5N1 infection has been responsible for the highest number of recorded cases of extremely virulent illness as well as the highest mortality rate. On three occasions it has jumped species to infect humans most recently in 2004 and our current trouble, but also in Hong Kong in 1997 when there were 18 infections and one third of them fatalities and also Hong Kong in 2003 with 2 cases and one death.
Two, and even more disconcerting is that the current H5N1 virus runs the risk of mutating, if enough chances are presented to it, into an infection of pandemic proportions. Thus far the H5N1 virus has displayed all the rudimentary qualities it needs to initiate a pandemic except one critical component, the capacity to be effectually transmitted from human to human. While currently the H1N1 virus is at the critical pandemic level, the potential for a pandemic to develop from a mutated human version of H5N1 virus must not be ignored.
The H5N1 virus can suddenly begin infecting people in two ways. The first is in an exchange process between viruses. The genetic matter is passed between a human and bird flu virus while there is a mutual infection of the two viruses with a person or a pig. This trade of material or shuffling process could mean the mutated result is a very dangerous and highly infectious pandemic virus and would be introduced into society by a rash of human cases and a rapid spread.
Another method would be slower but no less perilous, adaptive mutation is caused by the virus attaching to human cells in a steady manner through successive human infections and the virus becomes more capricious and pernicious as it gathers momentum forming small groups of human illness where there is confirmation of person to person contact. This second version of events would at least, if discovered early enough, give authorities some valuable time to respond.
In the Hong Kong H5N1 influenza spate of 1997, there were eighteen cases of illness which happened to take place when there was an outbreak of a far more severe and contagious bird flu by a virtually matching strain of the virus occurring on poultry farms and in public poultry markets. Intense follow up studies with familial and personal contacts of the patients, health care personnel, and those who culled flocks of birds determined there was little confirmation, in not any at all to confirm the spread between humans. In three days time, the culling of all poultry in Hong Kong ensured there was no further human infections. This at the expense of a million and a half birds that world medical officials credit with preventing a pandemic of avian influenza.
Everything up until now points to humans making contact with infected or dead birds as the primary source of illness in humans from H5N1 virus. People at risk are those who butcher, pluck feathers, initiate the bird kill process and those who process poultry meat for consumption when handling infected bird carcasses. Some individuals came into contact with chicken feces specifically using a poultry free range as a playground for kids and subsequently became ill. Experts also believe that swimming in water that contained dead bird cadavers or where infected birds could have contaminated with their droppings is potentially a further cause of some infections.
Not all cases of initial virus exposure could be indentified making authorities consider the possibility that some undiscovered infectivity factor with the virus may be the cause of certain cases. Some thoughts about what this cause may be area possible connection with feral birds such as pigeons or perhaps employing bird droppings as a form of fertilizer. For the time being H5N1 avian influenza is primarily a bird illness. The obstacle of single species strains of flu is noteworthy since the virus does not transfer from birds to humans without difficulty.
Notwithstanding the fact that there have been millions upon millions of diseased poultry in huge areas since the year 2003 there have only been less than a couple hundred cases of clinically diagnosed human H5N1 infection. There must be a reason, as yet not understood, why many of these infections occurred out in the country or semi rural locations where families and farmers maintain smaller stocks of poultry. It is also an anomaly that there are fewer infections in those groups that would ordinarily be considered at greater risk such as industrial poultry personnel, live poultry market vendors, those who cull flocks, veterinarians, health care workers who aid the patients that are ill, many not having the proper safety gear to do so without leaving them vulnerable.
There is also a lack of data or understanding of why kids who were in good health and medically fit young adults seemed to get ill. Health officials need to quickly discover logical reasons for this type of exposure. Are there certain behaviors involved? Perhaps there are immunity or genetic circumstances that seem to leave these groups vulnerable to infection?
Evaluating Potential infections in People
Examining many of the verified human infected with H5N1 virus, those in Asian nations and in Turkey, showed that direct contact with diseased avian species as presumably the primary reason for exposure. When reviewing likely infections, medical personnel should be inclined to look at those people displaying signs of influenza symptoms such as respiratory illness, hyperthermia etc. and those persons with a close proximity to birds. Particular attention should be paid to those presenting with these symptoms who reside in locations of verified outbreaks of the contagious H5N1 bird flu are active. If those presenting symptoms are from an environment where avian fecal matter may have caused contamination then than perhaps this would be a secondary consideration for exposure.
To this point, human infections of H5N1 virus are not all the responsibility of contact with diseased carcasses or tame bird stock that look like they are ill. In 2005 reports showed that domicile ducks could emit large amounts of high contagion virus but display none of the illness symptoms. There was no threat to people who ate poultry from these countries provided they cooked their poultry well and those people did not take part in prepping the food.
Since there is not a sign of any person to person spread of this virus anywhere, there is no discernable hazard for anyone travelling to these countries where outbreaks occur provided obvious precautions are taken such as staying away from open air poultry markets, farms or any other location where diseased bird contact is imminent or has occurred in the past.
How Clinical Symptoms Present
When a patient with H5N1 influenza becomes ill the infection is usually quite aggressive during its path, with patients displaying a fast decline with an elevated mortality. As with most new diseases, H5N1 influenza has a long learning curve for health officials. Health services data compiled in 1997 along with the latest epidemic are only now starting to illustrate the clinical characteristics of the infection yet there is so much left to study. Making matters worse is the fact that the virus has a habit of mutating quickly meaning its unpredictable nature makes disease mapping that much more frustrating for researchers.
The infection development phase for H5N1 avian flu is probably longer than the more common seasonal influenza which stand around two or three days. Any current information regarding disease incubation shows a range of two days to eight and quite probable extending to a length of seventeen days. But the Likelihood of numerous exposures to the H5N1 virus means accurately calculating a disease development period quite difficult. The WHO is currently saying clinicians should use a seven day gestation period in order to conduct examinations at ground zero for illness and when observing patient acquaintances.
The illness presents itself through elevated temperature, higher than 38° Celsius with influenza type indicators. Vomiting and diarrhea, stomach pain, chest pain and gum and nosebleeds have been cited as pre symptomatic signs with certain patients. Watery diarrhea with no blood seems more common in H5N1 than in the season variety of flu. The range of illness symptoms may be wider still. Verified patient illnesses have not all included respiratory problems.
Several Vietnamese persons infected the diagnosis was severe encephalitis: neither of these people showed any respiratory distress when they presented. Another infection in Thailand had the patient presenting with hyperthermia and diarrhea but no lung/breathing distress. In all three of these infected patients they had been in direct contact with diseased poultry.
A characteristic observed in a number of illnesses was the development of indicators in the lower respiratory tract in the beginning stages of the illness. Many patients display these lower respiratory symptoms when initially looking for treatment. Based on current knowledge, breathing irregularities begin to manifest about day five of the onset of illness. Respiratory trouble, hoarseness in the voice, and a discernable crackly noise while inhaling are most likely observed. Phlegm production is erratic and occasionally tainted with blood. Lately there have been bloody respiratory secretions seen in Turkey. Nearly all patients wind up with pneumonia.
Throughout the Hong Kong influenza illness spurt, the severely sick people showed primary viral pneumonia that antibiotics couldn’t help. Inadequate information about patients in the current outbreak show the signs of primary viral pneumonia in H5N1 that usually fail to show signs of bacterial supra-infection when determining diagnosis. Turkey medical officials have documented pneumonia as a consistent characteristic in more harsh cases, and the same as other patients, these people did not respond to being treated with antibiotics.
Those patients with H5N1 Influenza suffer a quick decline in their illness. There was a six day time period from the beginning of the flu to respiratory distress in Thai patients with an overall spectrum of four to thirteen days. Severe Turkish H5N1 illnesses the respiratory decline was three to five day after initial symptoms appeared according to medical experts. Something else which appears all too common is the irregular function of multiple organs. General laboratory anomalies, consisted of leukopenia (chiefly lymphopenia), mild-to-moderate thrombocytopenia, prominent aminotransferases, and with several occasions of disseminated intravascular coagulation.
There is some confirmation that particular antiviral medications, especially Oseltamivir or generic Tamiflu as it is known commercially, as they decrease the ability of the virus to reproduce thus improving the odds of survivability. They must be taken inside a forty eight hour window from the start of symptoms to be effectual. Data collected from the Turkish outbreak suggests that the majority of those with the virus were diagnosed and treated well into their course with the illness. It is because of this information that the use of Oseltamivir as a treatment is somewhat incomplete.
Oseltamivir or Tamiflu and other antiviral medications where produced as forms of treatment and as prophylaxis methods for seasonal variations of influenza, known to be a less severe version of flu as well as having a longer virus reproduction process in the body. The options for treatment courses and dosage quantities are still in a state of fluidity for oseltamivir – tamiflu therapeutic treatment of H5N1 influenza as it is with child illness of the virus. The WHO is continually monitoring and reviewing these antiviral practices as they require vital revision.
When a case of H5N1 influenza is suspected, generic tamiflu needs to be prescribed and taken as quickly as possible, preferably within forty eight hours from becoming symptomatic in order to optimize the value of the medication. Given the virulence of the current strain and the length of time of replication process, mortality rate etc. it would behoove the primary physician to begin treatment with generic Tamiflu also in those patients who are well into the illnesses course.
The existing suggested dosages for generic tamiflu for influenza virus treatments can be located on the Manufacturer – Roche’s website under product information. Currently the optional dose for generic tamiflu for influenza therapy is 150 mgs daily for children thirteen years and over and also adults, administered twice daily at 75 mg each for a course of five days minimum. There is no record of Tamiflu treatment for kids under one year old. The WHO health experts are looking into issuing treatment dosages and recommendations for children under the age of one year.
Since H5N1 viral reproduction periods could be extended, clinical personnel should reflect on increasing the tamiflu course treatment from five days up to seven or ten days in patients who are not responding to average treatment courses. When a patient displays severe H5N1 infection, they may want to raise the suggested daily dosage or length of treatment time. Clinicians also need to remember that Tamiflu dosages higher than 300 mg per day can be responsible for an increase in adverse effects . These same clinicians may want to consider administering serial clinical samples for future examination so viral loads can be monitored, an assessment can be made on medication susceptibility and levels of tamiflu can be reviewed. But, these samples should only be ingested where suitable procedures for infection control are available.
When a patient with H5N1 is suffering from a severe form of the illness and hampered by gastrointestinal symptoms, the absorption of Oseltamivir – Tamiflu could be hindered. Clinicians need to be cognizant of this prospect when treating patients such as these.