The viral infectious diseases pose a big challenges to public health as there are no effective measures to control the continuous spread of these diseases. Viral diseases are smarter than bacteria, as they spread in incomprehensible ways, difficult to understand and control.
Though they are known to cause causalities, recently they have started attacking human and livestock with a renewed vigour for e.g. Zika virus spreads by mosquito bite affecting pregnant women. The virus seriously cripple new born babies by mental disabilities with shrunken brain size and skull .The Epstein Barr virus spreads by mouth to mouth contact and is known as kissing viral disease.
The mortality and morbidity owing to viral diseases is on the rise , for example Chikungunya ,Dengue and H1N1.The diseases which are old and new are causing a huge burden on national economy and go on rampage seasonally killing several children and crippling the aged ones .There are only a very few well defined anti-viral drugs which can kill the virus like antibiotics. The viral attacks can lead to physical deformities and death causing a huge economic burden on government exchequer and on individuals.
The challenge before pharmaceutical industry is to conduct productive, cost effective research which can result in novel antiviral drugs and helps the management in viral diseases.
The viral infections were usually thought to be self-limiting. Initially the virus grows into a big infection in human system and activates the host immune system which kills the virus. In recent time the above behaviour viral infection has changed very much and the human beings and livestock are under a great threat of viral infection and the conditions. The majority of the viral diseases noticed so far have no proper chemotherapy agents and the scope of inventing the broad spectrum antiviral drugs and a discovery of an effective antiviral drug may be the new blockbuster drug in waiting.
Viruses are small particles either DNA or RNA that are surrounded by protein or fat coat. They are incapable of growing outside the living cell. They survive by infecting the individuals and enter the cytoplasm of DNA and growing inside the cell. Hence they are intercellular parasites. E.g.; -plasmodium causing malaria, TB causing bacteria are also intercellular parasites. Virus causes numerous diseases in individuals. They can affect various parts of the body including reproductive system, respiratory system, and GI tract. They can also damage liver, brain, spleen and they are also implicated as the causative organism of cancer. E.g. cervical cancer, papillomavirus.
Viral infection happens when the virus enters the host cell and utilizes genetic material to grow and multiply. Virus can infect the host by using internal mechanism of host cell and by eating up the genetic materials of the host cells, and making viral particles. After making a large number of viral particles within the host cell, the virus will break down the host cell itself and release millions of virus particles which can infect the new cells or when they are picked up by the vectors like mosquito can affect the other individual by the infected mosquito bite to the healthy individual. Certain viruses can be inactive or latent for several years and on change of internal environment they can become active and cause infections. Such virus are called static virus. e.g.: HIV
The viruses make more copies of itself by eating host cell DNA and RNA and also kill many host cells. In recent times the viral diseases are making many people ill and are also causing huge morbidity and mortality for e.g.: dengue, Chikungunya.
There are many viruses which are changing their pathogenesis and the way in which they spread is taken by surprise. The drugs for these diseases are not available and this leads to a large opportunity and challenge for the pharmaceutical scientists and researchers. The diseases which are becoming more and more prominent and pronounced are listed in the table (1.1).
The heavy toll of these diseases have compelled common man the search for the remedies to overcome the suffering and death. In that process for dengue diseases, people have found out the juice of papaya leaves can improve the platelet count and provide relief that offered to have a control over the vigour of the disease and diminish the symptoms. So like this many natural remedies like turmeric powder and all spices rich in antioxidants including garlic, onion and many spicy ingredients like cinnamon, clove are also tried . It is a challenge for the pharmaceutical industry to take a clue from above leaves by establishing scientific validity for the above claims further. It has to identify the active ingredients which are responsible for its antiviral activities after identification isolation and deciphering the chemical structure of active ingredients for development and evaluation of new molecular entity as antiviral drugs.
In many instances they are found to be effective but not sufficient enough to be used as effective treatments. Now the scientist can take from here to isolate the active ingredients known to be used as folklore medicines into new molecular entities and develop a scientifically based therapeutics to treat viral diseases. Existing antiviral drugs are usually aimed at killing and controlling HIV and hepatitis infections. Actually the existing drugs cannot be used to the treatment of the new viral infections. There is a tremendous scope and market awaits the discovery of new antiviral drugs.
There was a time when viral infections are to be prevented otherwise the causality was certain for example: the diseases caused by animal bites leading to rabies is one of them. The many viral diseases which are known to cause terrible morbidity and usually in infection could vanish within a week. .Hence , nobody took them seriously and in recent times the viral diseases have intensified in terms of morbidity and mortality. For ex: HIV , Hepatitis .
The challenge to develop the drugs is multifaceted for example the virus behaves like non-living entity and is difficult to kill them outside the cell. Virus entering a cell becomes live organism and utilizes the host living materials for its development and reproduction which is inside the cytoplasm or may be inside the nucleus of the cell. The antiviral drugs need to be delivered deep inside the cell to kill the live virus. Viruses are capable of understanding the toxic effects of the drugs and quickly change the biochemical pathways to circumvent the toxic effects of the drug thus attaining the drug resistance.
Viruses presents itself in variety of alleles hence, very difficult to target ta viral receptor. It is very difficult to develop effective vaccine for virus unlike bacteria even though a good vaccine is developed no time virus will change its proteins and become resistant to vaccines. The virus thus offers a formidable challenge for control and overcome the effect of the vaccines which can protect the human and prevent the morbidity and mortality caused by viral diseases.
The following viruses are known to be very dangerous and cause serious morbidity and mortality challenges in pandemic and epidemic fashion. So viral infections are known to effect from toe to head starting from skin infections, sexually transmitted diseases, hepatitis, gastritis, CVD, myelitis, gingivostomititis, pancreatitis, pneumonia, common cold, eye infection, fungitits, encephalitis, meningitis.
The viruses can be transmitted in a variety of modes and fashions for Eg; which are known to spread through touch, saliva, sexual contact, shaving of contaminated needles and blades and insects like ticks and mosquitos. They can also spread through food and cause infection to healthy individuals.
Rhino virus which causes common cold and symptoms like coughing, sneezing, mild headache, sour throat lasts for 14 days where as Viral influenza is a bit more serious condition caused by influenza virus and may cause flu with body aches and severe fatigue. The respiratory syncytial virus is known to effect whole respiratory system leading to bronchitis and pneumonia causing severe conditions in infants, small children, and aged people.
The skin infections include Mollscum contagiousm, herpes virus, varicella zoster virus, which cause itchy oozing blisters, fatigue, and high fever characteristic of chicken pox. The food borne viruses include Hepatitis A, Nora virus and rota virus, can cause food poisoning along with hepatitis symptoms include yellow skin also known as jaundice, diarrhoea and vomiting.
The rota virus can cause severe watery diarrhoea, leading to dehydration and death. Sexually transmitted viral infections spread through contact with body fluids. It includes human papilloma virus, a risk factors for cervical cancer, hepatitis B causes pain full sores and antiviral medications are found to be useful in containing the disease.
HIV is the causative virus for AIDS which is dreadful disease HIV is transmitted by blood or body fluids of an infected person. The HIV is known for weakening the immune system and leading to opportunities for infections and cancers. Lot of researches have been done in control and spread of this disease. There are a lot of information and application of the information for the management of HIV infections.
In spite of all these, HIV is spreading across the world. Similarly there are many viruses which are causing a global threat to the existence of human beings for E.g.; Zika virus, Chickungunya, Dengue and also Bird flu etc. There is a need for developing effective treatments for viral infections and anti- viral drugs will be the future determining factors of human health and life.
(Authors are faculty, SCS College of Pharmacy, Harapanahalli )