IN THE KNOW: Avian influenza

The avian influenza, or bird flu, is an infectious disease caused by type A strains of the influenza virus.

The various strains of avian flu may cause a mild form of the disease in birds, characterized by disheveled feathers, reduced egg production and mild effects on their respiratory system.

They may also cause a rare deadly form, which does not only affect respiratory tracts but also attacks multiple organs and tissues in birds.

Avian flu is transmitted from one area to another by the movement of birds, people with contaminated clothing, contaminated farm equipment and chicken feed, among others.

The H5N1 strain has posed threats to human health since its first reported human infection in 1997 during an outbreak in Hong Kong.

This strain is transmitted to humans through contact with infected birds. H5N1 is also spread through bird feces, which, when dried and pulverized, may be inhaled by humans.

Since its reemergence in 2003, this avian virus has spread from Asia to Europe and Africa, and has become entrenched in poultry populations in some countries.

There were 859 reported cases of human H5N1 virus infection from 16 countries from 2003 to 2017, according to the World Health Organization (WHO). WHO said 453 cases were fatal.

The first recorded bird flu case in the Philippines was in July 2005 in a small farm in Calumpit, Bulacan. It was found to be a “low-pathogen” strain and not harmful to humans.

The country has since implemented precautionary measures, such as strict bans on poultry imports from affected countries and surveillance of migratory birds.

The death of an overseas Filipino worker (OFW) after his return from China in 2015 was considered a possible case of avian flu due to his travel history, exposure to live poultry, the symptoms he showed and the quick progress of his condition.

After considering the danger of shedding the virus into the environment if an autopsy was performed, the Department of Health instead conducted a fully guided biopsy on the remains of the victim. The results were “inconclusive,” then Health Secretary Janette Garin said.

“The body was cremated, hence, this case has been declared closed,” she said, adding that there was no other way to safely confirm if the OFW had indeed died of bird flu.

A low pathogenic avian influenza virus, the H7N9 virus subtype, has been infecting birds and people in China. The strain first infected three humans in China in March 2013. In January this year, as many as 79 people have died from H7N9 in China bringing the total human death toll from the H7N9 strain to 100 since October last year.

Outbreaks across Europe and Asia have been ongoing since late last year, leading to mass culling of poultry in many countries. Strains currently documented as circulating in birds include H5N8 in many parts of Europe as well as in Kuwait, Egypt and elsewhere, and H5N1 in Bangladesh and India. —INQUIRER RESEARCH

Sources: Inquirer Archives, who.int