Bird Flu Resurgence

ByDr. Giovanni Tapang
Prometheus Bound / Manila Times

We spent the long break back at my hometown in Malolos where my ten year old nephew keeps his pets around. He has several of them including a brood of bantam chickens, a flock of pigeons, three dogs, and their ever present cats. One would wonder how easily it can become unweildy as the number of chickens, pigeons and other animals increase. Imagine this happening in a large scale with pigs, birds and humans as we interact with each species and each other in areas such as poultries and pig farms.

Recently the World Health Organization (WHO) noted that mutant strains of avian flu could again be spreading in some countries in Asia. Avian flu, or commonly called bird flu, is a virus influenza that can infect birds. Typically, avian influenza viruses do not infect other species. If they do, flu symptoms sometimes do not express themselves. However, there are times that some avian flu virus genes can be reasserted together with human flu virus genes inside an animal such as pigs or other poultry species) that are co-infected with both viruses. These produces new flu subtypes that can infect both humans and birds. Higly pathogenic avian influenza strains such as the H5N1 flu virus had been spreading throughout Asia since 2003.

The H5N1 virus was the cause of the loss of millions of poultry in Asia, Europe and Africa. In 1996, highly pathogenic H5N1 virus was isolated from a goose farm in Guangdong Province in China. A year later, outbreaks of H5N1 were reported at farms and animal markets in Hong Kong. Human infections were then subsequently reported in Hong Kong. Since then, the number of bird to human transmissions leading to severe infections have risen. Since birds and humans are vastly different, the virus does not easily cross over species but as of the latest WHO data this August, there were already 565 cases of human infections and 331 human deaths from this virus.

The virus has now spread to many countries. It has also been observed in some cases to cause a broader spectrum of disease than flu. Other mammals such as domestic cats which catch and eat birds were also shown to be susceptible to this strain. An outbreak in zoo tigers fed with chickens happened in Thailand in 2004. In 2005, wild birds began dying in a lake in Central China where migratory birds congregate.

Research from samples taken from this outbreak suggests that a new more lethal H5N1 variant caused the die off.

Its landing in Europe was reported first by Russia and Kazakhstan in mid-2005. Later it was found in Turkey, Romania and Croatia. In November 2005, Kuwait marked its first reporting in the Middle East. A few months later in February 2006, Nigeria reports the first case of H5N1 in Africa. Research have suggested that apparently healthy migratory birds can carry the virus over long distances. This has been pointed out as one of the ways the virus can travel long distances. The virus reached US shores from wild swans in August 2006. The bird flu have mortally infected more than 300 humans in Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Laos, Nigeria, Pakistan, Thailand, Turkey, and Vietnam. It has also caused the culling of nearly 400 million of birds since 2003. The economic impact of this flu is estimated to be around USD 20 billion and still rising.

Health concerns have led to banning the sale of live birds in markets as well as closer monitoring of poultry farms all over the world. The fear is that a new mutation in the virus can make it easier to pass on from human to human. The monitoring that the WHO is doing is precisely to preempt this spread and prevent another pandemic.

The wide extent to which the virus infected the world is mainly due to the nature of the virus itself and its carriers. Wild birds have long ranges that do not recognize national boundaries. Their air corridors can span several countries and these flocks stop at feeding grounds, water sources and foliage as they move around the world. We also maintain large poultries that can get infected easily. On the other hand, flu viruses mutate very rapidly. They can change their protein and sugar coatings so easily such that vaccines are only as good against the strain it was designed for.

While the Philippines might not be as hard hit as other countries with regard to the bird flu, the sad state of health services in the country gives us cause to worry. The proposed health budget for 2012 is still far from the 5 percent of GNP WHO recommendation that should be allotted to health services. With the recent warning from the WHO is that avian flu has shown signs of resurgence, it is imperative that government should allocate as much to strengthen its public health system.