Several reports of bird flu (H5N1) outbreaks have recently been made in the states of Gujarat and Maharashtra. Outbreaks at this point appear isolated although state health departments are issuing warnings to prevent further spread across states.
These outbreaks have primarily occurred in smaller towns, though reports have indicated the virus is present in Ahmedabad. This has sparked concerns of exposure to a larger population as well as a higher potential for spread of the disease. This is the second case of an outbreak in the city, the first occurring in 2006.
While the disease is prevalent in avian species, there is the potential for cross contamination to human hosts in situations where exposure is high. In the 2006 Ahmedabad outbreak, only one associated death was reported: Ganesh Sonarkar, a poultry farmer from the Nandurbar district.
While this may seem a small death toll compared to the many other contagious diseases affecting India, it is the potential of a large scale outbreak that has warranted the culling of livestock and regulated zones currently in place within the city. While transmission rates to humans is very low, and spread between human hosts almost unheard of, the associated mortality rate is stated by the World Health Organization (WHO) to be around 60%.
Concern primarily stems from the ability of lytic RNA viruses (of which all forms of influenza fall under) to mutate. Mutations are the cause of the varying strains of flu, and a consistent issue as individual vaccines are not effective against all strains. H5N1 in particular is considered a priority due to its high mortality rates. A 2009 study in the Journal of Theoretical Biology suggests that bird flu could reach pandemic levels in a human population.
Mutation of the virus could occur in two ways. One of these is spontaneous mutation, a result of errors in the genome after replication. This is a very common occurrence in lytic RNA viruses, proposed to be one base change per genome, per replication (put simple, a single portion of the genetic code of the virus changes each time it replicates). As viruses are present in such high numbers (thousands may be synthesised in each cell) the rate of mutation is high, hence the necessity to cull and quarantine infected birds to limit host organisms.
The second possibility is that genetic reassortment (in which two viruses exchange sectiosn of their genetic code) takes place in an individual infected with both bird flu, and a less deadly, but more transmissible strain of the flu such as H1N1 (spanish flu, swine flu). With both viruses present in a human cell the potential is created that genetic material is shared. The possibility then occurs that a mutated H1N1 virus, easily transmitted between human hosts, now contains the portion of the genome from H5N1 responsible for the high mortality rate. This situation would result in a highly contagious strain of the flu with a mortality rate of up to 60%.
In the south of the country in Tiruvallur in the state of Tamil Nadu a potential outbreak of H1N1 was reported.After medical examination of 26 people it was found that 25 tested negative for the flu, instead being diagnosed with respiratory tract infections or viral pneumonia. One patient was diagnosed with the flu but is now under treatment at the Institute of Child Health in Egmore.
For now, the situation in all affected states is being appropriately addressed, with the sick in hospital and potential for infected livestock being monitored. Another viral outbreak is something India cannot afford and so such precautions are more than necessary.