Virology Of Influenza Virus : Microbiology Review Symptoms
Every year, influenza epidemics cause numerous deaths and millions of hospitalizations, but the most frightening effects are seen when new strains of the virus emerge from different species
(e.g. the swine-origin influenza A/H1N1 virus), causing world-wide outbreaks of infection (WHO. 2012). Several antiviral compounds have been developed against influenza virus to interfere with specific events in the replication cycle. Influenza virus has caused seasonal epidemics and worldwide pandemics, which caused tremendous loss of human lives and socio-economics (Holmes et al., 2005; WHO. 2012).
The current contagious outbreaks of respiratory disease which has begin to aroused a really great concern on potential global pandemic outbreak, which would take toll of millions of human lives. Most of those acute outbreaks are caused by newly emerging viruses, such as highly pathogenic avian influenza virus H5N1 in 1997, bat-origin SARS corona-virus hCoV (SARS-CoV) in 2003, swine-origin influenza virus (pdmH1N1) in 2009, novel SARS-like coronavirus hCoV-EMC in 2012 and 2013, and even the avian-origin influenza virus (H7N9) in 2013 (Jit et al., 2013). Notably, influenza viruses struck human most frequently, and had already caused at least 20 million deaths in 1918 worldwide (Spanish flu). Wild birds are the natural reservoir of influenza viruses, and they migrate regularly around the world every year, making them the best virus transporter for airborne viral-transmission (CDC. 2006). An avian strain can adapt to the human host and attain human-to-human transmission capability through acquired mutations. There are some human adaptation that are unexpected when it comes to influenza subtype or maybe the strain rather than the currently circulating influenza viruses that has cause pandemic flu (Jit and Beutels, 2012).
Influenza, commonly known as “the flu”, is an infectious disease caused by the influenza virus (Holmes et al., 2005). Symptoms can be mild to severe (Ahmed et al., 2013). The most common symptoms include: a high fever, runny nose, sore throat, muscle pains, headache, coughing, and feeling tired. The influenza symptoms can typically start within a space of two days after a terrible exposure to the influenza virus and then a most last that would be less than a week. The cough which is a symptoms can hold you down, however, the symptoms may in so many occasion last for more than two weeks on the minimum (Holmes et al., 2005). In kids there can be signs of nausea and then it may get to vomiting, but these type of symptoms are not so common in cases involving adults. Nausea and vomiting mainly occur in most unrelated infection gastroenteritis, these are sometimes inaccurately called “stomach flu” or “24-hour flu” (Jefferson et al., 2012).
Complications surrounding influenza has been included as a viral pneumonia, or sinus infections, the secondary bacterial pneumonia and also the worsening of previous health problems which includes asthma or may lead to heart failure (Ahmed et al., 2013; Beigel and Bray, 2008).
Three types of influenza affect people (Beigel and Bray, 2008). Usually, the virus is spread through the air from coughs or sneezes (Holmes et al., 2005). This is believed to occur mostly over relatively short distances (Kash et al., 2006). It can also be spread by touching surfaces contaminated by the Influenza Virus and then touching the mouth or eyes (Smith et al., 2006). A person may be infectious to others both before and during the time they are sick (Holmes et al., 2005). The influenza infection can still be confirmed through the testing of the throat, sputum, or nose for the influenza virus. A number of rapid tests are always available; however, people may still have the infection if the results are negative. A type of polymerase chain reaction that detects the virus’s RNA is more accurate (Kobasa et al., 2007).
Frequent hand washing reduces the risk of infection because the virus is inactivated by soap (Winther et al., 2008). Wearing a surgical mask is also useful (Winther et al., 2008).Yearly vaccination against influenza is recommended by the World Health Organization in those at high risk (Beck et al., 2012). The vaccine is usually effective against three or four types of influenza. It is usually well tolerated. Most of the vaccine are made for one year which cannot be as useful in its next year, because the influenza virus can still evolves rapidly. Antiviral drugs such as the neuraminidase inhibitors oseltamivir among others have been used to treat influenza (Beck et al., 2012).Their benefits in those who are otherwise healthy do not appear to be greater than their risks (Beck et al., 2012; Udell et al., 2013). No benefit has been found in those with other health problems.
Influenza has been reported to have spreads around the world on a yearly basis, since the outbreak has been hard to contain, this has resulted in about three to five million situation of severe illness and has led to about 250,000 to 500,000 deaths cases (Jefferson et al., 2010). In the Northern and Southern parts of the world outbreaks occur mainly in winter while in areas around the equator outbreaks may occur at any time of the year (Jefferson et al., 2010). Death occurs mostly in the young, the old and those with other health problems (Jefferson et al., 2010). Larger outbreaks known as pandemics are less frequent (Gooskens et al., 2009). Earlier in the 20th century, there were three influenza pandemics which has occurred severally: the Spanish influenza in the year 1918, also the Asian Influenza Virus in the 1958, and then the well documented Hong Kong influenza in the 1968, each has resulted in at least in more than a million deaths (Weber and Stilianakis, 2008). The World Health Organization declared an outbreak of a new type of influenza A/H1N1 to be a pandemic in June of 2009 (Udell et al., 2013). The Influenza Virus may also affect other animals including: pigs, horses and birds (Jefferson et al., 2010).
Signs And Symptoms Of Influenza
Approximately 33% of people with influenza are asymptomatic (Cheung et al., 2002). Symptoms of influenza Virus can start quite suddenly one to two days after infection. Usually the first symptoms are chills or a chilly sensation, but fever is also common early in the infection, with body temperatures ranging from 38 to 39 °C (approximately 100 to 103 °F) (Schmitz et al., 2005). Many people are so ill that they are confined to bed for several days, with aches and pains throughout their bodies, which are worse in their backs and legs (Wintheret al., 2008). Symptoms of influenza may include:
- The fever and extreme cold couple with chills shivering and the shaking
- Cough, Nasal congestion and Runny nose
- Sneezing, Headache and Irritated, and watering eyes
- Body aches, especially joints and throat
- Reddened eyes, skin (especially face), mouth, throat and nose
- Petechial rash (Thomas et al., 2008).
In children, gastrointestinal symptoms such as diarrhea and abdominal pain (Nicholls et al., 2008; Korteweg et al., 2008), (may be severe in children with influenza B) (Schmitz et al., 2005)
It can be difficult to distinguish between the common cold and influenza in the early stages of these infections (van Riel et al., 2005), but this flu can easily be identified through the high fever couple with the sudden onset and also the extreme fatigue that sets in. Influenza is a mixture of symptoms of common cold and pneumonia, body ache, headache, and fatigue. Diarrhea is not normally a symptom of influenza in adults (Bean et al., 2002), although it has been seen in some human cases of the H5N1 “bird flu” (Nayaket al., 2004) and can be a symptom in children (Nicholls et al., 2008). The symptoms most reliably seen in influenza are shown in the table to the right (Shinya et al., 2006)
Since antiviral drugs are effective in treating influenza if given early (see treatment section, below), it can be important to identify cases early. Of the symptoms listed above, the combinations of fever with cough, sore throat and/or nasal congestion can improve diagnostic accuracy (Drake, 2003). Two decision analysis studies (Pinto et al., 2006 Kash et al., 2006) suggest that during local outbreaks of influenza, the prevalence will be over 70% (Kash et al., 2006), and those victims with these different types of symptoms can still be treated with the neuraminidase inhibitors without any sorts of testing. Even the absence of any local outbreak in records, these treatments can be justified in the elderly during the influenza season as long as the prevalence is over 15% (Kash et al., 2006).
However, all the laboratory tests mainly for influenza has continued to improve as time goes on. The United States Centers for Disease Control and Prevention (CDC) maintains an up-to-date summary of available laboratory tests (Liu et al., 2011). Reports from the CDC, suggest that a rapid diagnostic tests can have up to a sensitivity of 70–75% or even a specificity of 90–95% when they are compared with the viral culture. These tests may be especially useful during the influenza season (prevalence=25%) but in the absence of a local outbreak, or peri-influenza season (prevalence=10% (Kash et al., 2006)).
On the more serious side, influenza can occasionally cause either direct viral or secondary bacterial pneumonia (Hall, 2007; Thomas et al., 2008). The obvious symptom is trouble breathing. In addition, if a child (or presumably an adult) seems to be getting better and then relapses with a high fever, that is a danger sign since this relapse can be bacterial pneumonia (Carrat et al., 2008).