The H7N9 Group of Viruses - Research Paper Example

? H7N9- Disease and Epidemiological findings The H7N9 group of viruses is a subgroup of a larger group of avian influenza virus A H7. These viruses are usually found in birds and the source for the H7N9 virus is currently being investigated with many studies pointing to infected birds from poultry houses. The previously known subgroups of this group include the H7N2, H7N3 and H7N7 and these have been linked to human infections in many parts of the world. The current strain of H7N9, which has been confirmed to have infected about 82 people in China, is considered to be more virulent that the previous strains of H7 viruses that have infected humans. The viral sequences of the strain are being studied in labs across the world and scientists have determined that the hemagglutinin protein of H7N9, which binds to sialic acid molecules present in human cell surfaces, has a stronger affinity for its target receptor compared to those of other H7 viruses (World Health Organization (WHO), 2013; Li et al, 2013; Yandell, 2013). From the epidemiological standpoint older people have been found to be more susceptible to the virus with a majority of those infected being men. The disease was confirmed by various methods that included isolating the virus strains, serological testing and nucleic acid detection. The infection has been found to manifest with respiratory tract diseases and progressive pneumonia (WHO, 2013; Li et al, 2013). A majority of those infected have reported recent exposure to animals and till date there has been no indication of human to human transmission of the virus (Centers for Disease Control and Prevention (CDC), 2013; Li et al, 2013). The major treatment modalities tested under laboratory conditions have shown that the viruses were sensitive to anti-influenza drugs such as oseltamivir and zanamivir which are neuraminidase inhibitors. Hence the government has recommended that those suspected to have been infected with the virus should be administered either of these two drugs at the earliest once the symptoms appear even if the laboratory investigations are delayed (CDC, 2013; Li et al, 2013). The newest avian virus H7N9 that has infected humans in mainland China is a subgroup of a larger group of avian influenza A viruses known as the H7 viruses. The earlier viruses that were part of this group include the H7N2, H7N3 and H7N7. Other groups of influenza viruses include H5N1 and H1N1. All these viruses have affected humans in the past with the H5N1 and H1N1 successfully adapting to humans which resulted in a pandemic disease. These viruses are generally passed among birds and have been shown to affect animals and humans in the past. The source of these infections has been largely associated with infected poultry (WHO, 2013; Horby, 2013). The current H7N9 virus is being viewed as a highly virulent virus by epidemiologists compared to its earlier predecessors as it has readily spread to humans and has been found to cause life-threatening symptoms in severe cases (Yandell, 2013). The exact source of the virus is still being investigated with recent studies pointing to live market poultries near the areas where the cases of infections have been reported. Birds from six markets were tested for the virus and out of which few chickens and pigeons have been shown to carry the virus. While some of those infected have reported to have been exposed to poultry others have not reported any such exposure. Thus research is still underway to determine whether these viruses are being transmitted only from birds or the possibility of animal sources. In addition, as these viruses have not caused any major symptoms in birds or animals determining the sources is becoming increasingly difficult (Horby, 2013). Virologists in the Chinese National Influenza Center have determined the genetic sequence of the H7N9 virus from isolates collected from infected humans. They have found that the sequences closely resemble those of the other avian viruses and the genetic source has been attributed to multiple viral ancestors. Genetic studies have further revealed several mutations within the genes that could possible explain its ability to infect humans and cause more severe symptoms compared to the previous flu viruses. The genetic studies also revealed that the hemagglutinin molecules of the virus possessed increased affinity to the sialic acid receptors present on the human cell surface. Mutations have also been detected in the gene PB2 that codes for the RNA polymerase enzyme which could possibly explain the high rate of viral replication within the human body. A similar mutation in the PB2 gene was also found in the H7N7 viral outbreak in the year 2003. Epidemiologist Marion Koopmans has provided two possible explanations on how these mutations arose. These mutations that have resulted in increased potency could have occurred while the viruses circulated among birds and the virulent strains could have caused infection in humans. Another possibility is that the mutations could have occurred in vulnerable humans and given rise to severe symptoms (Yandell, 2013). The most common symptoms presented by infected individuals are respiratory illness which manifests as pneumonia along with fever, cough and shortness of breath. Mechanical ventilation has been provided to most patients with a severe form of the disease (WHO, 2013). The epidemiological characteristics of those infected with the virus in the Shanghai, Zhejiang, Jiangsu, Anhui, Henan and Beijing provinces of China are as follows. The median age of the patients was found to be 63 years with a majority being men. Most of the cases have been reported from urban areas. Increased incidence has been observed among the elderly and those who already have an underlying medical condition. About 21% of individuals infected with the virus have died due to acute respiratory distress syndrome with about 60 patients in a critical condition and the mortality rate is expected to rise given the critical condition of the remaining patients. The viral infection was confirmed using virus isolation, serological testing and nucleic acid detection by reverse transcriptase- polymerase chain reaction methods. Among those confirmed with the disease 77% reported recent exposure to animals with most of them visiting live poultry markets. The animals to which most of the individuals were exposed include chicken, ducks, swine, pigeons, geese, wild birds and pets such as cats and dogs. As with human to human transmission of the virus three family clusters have been reported from two provinces (Li et al, 2013). With increasing number of mortalities associated with the condition it leaves little doubt that the current strain of H7N9 virus is more virulent compared to the previous H7 viruses. The symptoms in the previous cases involved only mild illnesses such as conjunctivitis and a milder sign of influenza and only one fatal case was reported involving the H7N7 virus. The increasing fatalities and critical nature of the disease associated with H7N9 is proof for the highly virulent nature of the strain. As humans have only been recently infected with the virus the immunity for the virus is also expected to be low. As the poultry animals infected with the illness have shown minimal symptoms identification of the exact source of viral infection has become a daunting task. Only when the potential source is identified control measures such as banning the sales of infected poultry, disinfection strategies and other measures to stop the spread of the virus can be undertaken (Li et al, 2013). The government has recommended that immediate antiviral treatment be provided for those infected with the disease. Genetic studies conducted on the virus have revealed that they are resistant to the hydrocarbon derivative adamantine that functions by preventing the release of the viral genes in to the host cells for further replication. The viruses were however found to be sensitive to neuraminidase inhibitors that cause the virus to be trapped within the host cells by preventing the budding process (Yandell, 2013). The centers for disease control and prevention (CDC) has issues guidelines for the treatment of confirmed and suspected cases with the viral infection. The non-availability of vaccines for the disease, increased mortality rate associated with severe cases and the possibility of a human to human transmission as a result of the virus adapting to the human body has convinced experts to recommend treatment with antivirals at an early stage. Further studies have also shown that when antivirals are given earlier on following disease identification, the duration and complexity of the disease symptoms are reduced. The CDC has further recommended that clinicians need not wait for laboratory confirmation of the disease and when the patient present with obvious symptoms, or are at increased risk of developing the disease like the elderly, those with an underlying medical problem, young children and pregnant women antiviral treatment should be initiated immediately. Currently two neuraminidase inhibitors are recommended to treat the diseases namely oseltamivir and zanamivir. For those presenting with lesser complications and devoid of any major symptoms such as fever, clinicians can decide on the treatment initiation. As zanamivir is inhaled it is not recommended for those with respiratory problems such as asthma or chronic obstructive pulmonary disorder. In case of immune-suppressed individuals a higher dosage of the antivirals can be considered as the chances of prolonged replication of the virus and development of resistance to antivirals is more in these individuals. In cases of malabsorption of oseltamivir due to underlying gastric problems intravenous administration of zanamivir can be considered (CDC, 2013). In conclusion, infection with H7N9 virus warrants immediate treatment considering the increased virulence nature of the virus, mortality rate and the possibility of stably adapting in humans which could give rise to a pandemic disease. In addition, suitable steps need to be taken to identify potential sources of infection as they have to be controlled in order to prevent further propagation of the disease. References 1. Centers for Disease Control and Prevention (CDC). (2013, April 23). Avian Influenza A (H7N9) Virus. Retrieved April 28, 2013, from http://www.cdc.gov/flu/avianflu/h7n9-virus.htm 2. World Health Organization (WHO). (2013). Influenza- Avian Influenza A (H7N9) Virus. Retrieved April 28, 2013, from http://www.who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html 3. Li et al. (2013, April 24). Preliminary Report: Epidemiology of the Avian Influenza A (H7N9) Outbreak in China. The New England Journal of Medicine, doi: 10.1056/NEJMoa1304617. Retrieved April 28, 2013, from http://www.nejm.org/doi/full/10.1056/NEJMoa1304617#t=articleTop 4. Yandell, K. (2013). Characterizing H7N9. TheScientist. Retrieved April 28, 2013, from http://www.the-scientist.com/?articles.view/articleNo/35329/title/Characterizing-H7N9/ 5. Horby, P. (2013). H7N9 is a virus worth worrying about. Nature, 496(7446): 399. Retrieved April 28, 2013, from http://www.nature.com/polopoly_fs/1.12853!/menu/main/topColumns/topLeftColumn/pdf/496399a.pdf Read More