Viral infections influenza

Bacterial and viral myositis is well recognized as a clinical entity by muscle pathologists. The viruses most commonly involved appear to be the Coxsackie viruses, the arboviruses, influenza virus, and HIV, but the mechanism whereby the viral infection gives rise to the myositic syndrome is not known. A detailed discussion of such problems is presented later on pages 333-334. 

In pharmacology, two adamantane derivatives. Amantadine (1-adamanta-neamine hydrochloride) and Rimantadine (a-methyl-1-adamantane methyla-mine hydrochloride) (see Fig. 24), have been well known because of their antiviral activity [129]. The main application of these drugs is prophylaxis (treatment to prevent the onset of a particular disease) and treatment of influenza-A viral infections. They are also used in the treatment of parkinsonism and inhibition of hepatitis-C virus. Memantine (1-amino-3,5-dimethyladaman-tane) (see Fig. 24) has been reported effective in slowing the progression of Alzheimer s disease [130]. 

Although viral infections are important causes of both otitis media and sinusitis, they are generally self-limiting. Bacterial infections m complicate viral illnesses, and are also primary causes of ear and sinus infections. Streptococcus pneumoniae and Haemophilus influenzae are the commonest bacterial pathogens. Amoxycillin is widely prescribed for these infections since it is microbiologically active, penetrates the middle ear, and sinuses, is well tolerated and has proved effective. 

Catechins and proanthocyanidins have a documented antiviral activity. Catechins from an extract of Cocos nucifera husk fibre exhibited a strong inhibitory activity against acyclovir-resistant herpes simplex virus type 1 (HSV-l-ACVr) [62]. The use of 10 to 20ngml of ECG and EGCG has been reported to cause 50% inhibition of human immunodeficiency virus reverse transcriptase [89], while Kara and Nakayama [90] reported that a patented chewing gum containing tea catechins is claimed to prevent viral infections against influenza and to inhibit dissemination of this virus. 

Vaccination against hepatitis A and B is recommended in patients with underlying cirrhosis to prevent additional liver damage from an acute viral infection.35 Pneumococcal and influenza vaccination may also be appropriate and can reduce hospitalizations due to influenza or pneumonia. 

The adamantane moiety is of medicinal chemical interest because of its inertness, compactness relative to lipid solubilizing character, and symmetry. Considerable interest, therefore, was engendered by the finding that amantadine (78) was active for the chemoprophylaxis of influenza A in man. There are not many useful chemotherapeutic agents available for the treatment of communicable viral infections, so this finding led to considerable molecular manipulation. The recent abrupt end of the National Influenza Immunization program of 1976 prompted a new look at the nonvaccine means for prophylaxis or treatment of respiratory tract infections due to influenza A, especially in that the well-known antigenic shift or drift of the virus obviates usefulness of the vaccine but not amantadine. 

Neuraminidases are enzymes present in viruses, bacteria, and parasites. They are implicated in serious diseases such as cholera, meningitis and pneumonia. Neuraminidase from influenza virus aids the transmission of the virus between cells and maintains viral infectivity. In different strains of influenza several amino acids are conserved, especially in the active site, giving rise to hopes of finding a single inhibitor (and so a drug) for all the neuraminidase enzymes from influenza strains. The crucial question is whether a covalent bond is formed between the enzyme and the reaction intermediate. 

Despite the protective effect of NO against various viral infections, workers in several studies have shown a harmful role of NO in many systems. NO seems to play a part in the development of pneumonia caused by influenza virus [128], in the pathogenesis in mice of tick-borne encephalitis flavivirus infection [131], and in worsening the course of the murine myocarditis caused by coxsackievirus B3 [132]. In addition, pneumonia in mice induced by herpes simplex virus type 1 could be suppressed by the inhibitor of iNOS [133]. The issue of whether NO acts as an inhibitor of viral replication or as a harmful agent, therefore, remains unanswered. This issue is particularly evident in HIV-1 infection, since NO seems to act as a double-edged sword in the pathogenesis of HIV-1. 

Asthma Adverse reactions occurring in more than 3% of patients include headache and influenza. In children 6 to 14 years of age, the following events occurred with a frequency of 2% Diarrhea, laryngitis, pharyngitis, nausea, otitis, sinusitis, viral infections. In children 2 to 5 years of age the following events occurred with a frequency of 2% Rhinorrhea, otitis, ear pain, bronchitis, leg pain, thirst, sneezing. 

Influenza A viral infection Amantadine is indicated for the prophylaxis and treatment... 

Although infections are generally thought to be particularly frequent and possibly severe in patients treated with steroids, they have been used as short-term adjunctive therapy to reduce the severe symptoms associated with such bacterial infections as acute H. influenzae and miliary tuberculosis and in viral infections, such as hepatitis and infectious mononucleosis. 

FIGURE 11-24 Fusion induced by the hemagglutinin (FIA) protein during viral infection. HA protein is exposed on the membrane surface of the influenza virus. When the virus moves from the neutral pH of the interstitial fluid to the low-pH compartment (endosome) in the host cell, HA undergoes dramatic shape changes that mediate fusion of the viral and endosomal membranes, releasing the viral contents into the cytoplasm. 

This chapter describes the basic characteristics of viruses and the relatively limited number of drugs that can act selectively as antiviral agents. Methods of preventing viral infections (antiviral vaccines) are also briefly discussed. Finally, the current methods of treating a specific viral-induced disease—AIDS—are presented. Rehabilitation specialists often treat patients who are in the active stages of a viral infection, as well as those suffering from the sequelae of viral disorders, such as gastroenteritis, encephalitis, and influenza. Hence, the pharmacotherapeutic treatment and prophylaxis of viral infections should concern physical therapists and occupational therapists. 

At present, vaccines are available for several serious viral infections, including polio, smallpox, rabies, measles, mumps, rubella, hepatitis A and B, and influenza. In some situations, vaccination against certain viral infections is routine. For instance, schoolchildren must periodically show evidence of polio, measles, and other vaccinations according to state and local laws. In other cases, vaccines are administered prior to potential exposure to the virus or in high-risk groups. Influenza vaccinations, for example, are often administered to elderly and debilitated patients during seasonal influenza outbreaks.75,109... 

Respiratory syncytial virus (RSV) infection is a major cause of bronchiolitis in infants, whereas influenza A infection usually manifests as an upper respiratory tract infection. The immunological responses of infants to RSV infection and influenza A infection are different. In our studies of the cytokine responses during these infections, we found that the serum concentrations of IL-4, IL-5, RANTES, and soluble intercellular adhesion molecule-1 (sICAM-1) in infants with RSV infection were significantly higher than those with influenza A infection (S8). The concentration of TNF-a in nasopharyngeal aspirates was significantly lower in infants with RSV infection. Therefore, a predominant T helper cell type 2 (Th2) cytokine and related immunological response was observed in infants with RSV infection, whereas a predominantly proinflammatory cytokine response was observed in infants with influenza A infection. This may explain the different clinical manifestations of the two viral infections in infants (S8). 

Pujol et al. in chapter eight, reviews the chemistry, origin and antiviral activities of naturally occurring sulfated polysaccharides for the prevention and control of viral infections such as HIV-1 and -2, human cytomegalovirus (HCMV), dengue virus (DENV), respiratory syncytial virus (RSV), and influenza A virus. 

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