The Flu or influenza is caused by influenza virus. Influenza A virus spreads throughout the world usually because of the migration of birds. These strains are resistant to human immunity which is acquired for the other strains, this may result into an epidemic. Influenza virus also spreads by touching the contaminated surfaces and then touching mouth or nose. To prevent this, early vaccination is recommended which is effective against three to four influenza viruses.

In an infected stage, host uses two strategies to deal with it i.e. by reducing pathogen impact through which a tolerant host regains fitness or by eliminating the pathogen by which the resistant host can regain fitness. If the host is not able to tolerate or reduce the pathogenic burden, he or she is more susceptible to the infection.

The common symptoms of influenza are respiratory illness such as cough, fever, running nose, sore throat etc. Few people may have respiratory illness but others symptoms may be absent. Traditionally conventional viral cultures are used as standard for diagnosis of influenza which is used as a method of comparison for commercial assays. Rapid culture techniques are in practice for respiratory viruses.

The most effective way to prevent the infection of influenza virus is vaccination. Planning the supply of vaccines for healthcare is very important along with the development and production of the vaccine. WHO has been collaborating with scientists on global level for developing, manufacturing and testing and also distributing the influenza vaccine for efficient use for more than 50 years.

Development of new drugs against influenza has been of great interest. Number of drugs show Anti-influenza properties, but may have altered effects for the use in clinic. These drugs target viral components and some target the host cell elements which help in the viral cycle, but related side effects are the disadvantages. As for now, four antiviral drugs have been discovered against influenza; zanamivir and oseltamivir which inhibit neuraminidase which act in both Influenza A and Influenza B, while rimantadine and amantadine block M2 passage of influenza A.

A continuous antigenic drift is observed in influenza virus, Therefore vaccines that are to be used should be designed periodically for different strains of viruses along with the wild type of viruses which are found in particular season. Preparation for the pandemic which may result from antigenic shifts that are currently unavailable in human population is necessary.
 

Infectious diseases which are spread between humans and animals are known as zoonotic diseases. These are generally caused by fungi, microbes, parasites etc. which may result into illness in animals and humans which may even have mortal effects. Few animals may be the carrier of such pathogens, they may not be the sufferer but the people coming in contact with these animals may be sick.

Developing zoonotic ailments have possibly genuine human wellbeing and monetary effects and their current upwards slants are probably going to proceed. Cases are avian flu, Bovine Spongiform Encephalitis (BSE) and the Nipah infection. A portion of the "waiting" zoonoses are re-rising in a few districts, in spite of the fact that they appear to draw in less open mindfulness. Brucellosis, puppy rabies and parasitic ailments, for example, cysticercosis/taeniasis and echinococcosis/hydatidosis for instance.

Mostly people are infected by direct contact with the infected animals, by eating them or being bitten by them or the insect that has been in contact with the infected animal recently. In some cases people are infected by coming in contact with contaminated soil or water. Food is one of the chief sources of zoonotic diseases. Eating infected food with parasites such as bacteria, salmonella and tapeworms has resulted in millions of infections each year.

Influenza virus consists of eight ssRNA segments coated with viral nucleoproteins molecules which represent beads on string model. The size of these segments is approximately ~0.9 to 2.3 kb and the total genome size is 13.5 kb approximately. The viral RNA genome consists of 12 and 13 conserved nucleotides at 3` and 5` ends which bind to each other and form a pan-handle like structure associated with RNA polymerase.

Human medicine has not discovered the role of animals in transmission of zoonotic diseases same as veterinary medicine do not insure clinical features of human disease. It is necessary that physicians and veterinarians work hand in hand to control the zoonotic diseases. Physicians usually do not study the importance of animals in disease transmission whereas the veterinarians lack the training in aspects of clinical trials of human diseases.

Tracking and listing the information gathered from diseases observed in domestic and wild animals with humans suffering from illness is important. We can attain control in preventing and minimizing the impact of infection that can come into contact with such outbreaks if we have proper knowledge about the infection. People with compromised immunity such as people suffering from AIDS or those are chronically ill are at higher risk of such diseases. To decrease the risk of zoonotic diseases strict guidelines must be followed

Disease surveillance is basically collection, distribution, dissemination of information and interpretation of a particular disease. Surveillance is important as it can help in detecting the occurrence of disease which will benefit in reducing the economic loss, the sickness and mortality which can be attained by integrating animal and human health system. It will also help in making inventions that can control the outbreak of zoonotic disease.

The vaccine production market is one of the most profitable investment options. Increase in number of pet owners, and their concern about maintaining good animal practices are the other reason for the market growth. But on the other hand, government intervention in distribution channel is responsible for the loss of vaccine productions. Purchasing vaccines in bulk for livestock supply are resulting in decreasing the revenue margins of vaccine producers by bulk pricing.

Increase in livestock diseases and increasing populations has resulted in growth of market. Awareness about vaccination has escalated, but the consequence is higher costs of storage of vaccine has opened gates for many new ideas thus making a way for new entrepreneurs.

People who are in contact with animals, agricultural workers, slaughterhouse workers, ranchers, veterinarians are in high risk of being infected by zoonotic disease.  Teaching correct diagnostic techniques about zoonotic diseases to the livestock owners and other people which are in contact with animals can help in reducing the outbreak of disease.