Avian influenza: transmission, impact, and public health response

Health-Nursing

Avian Influenza

Avian Influenza is a disease that humans are becoming exposed to through contact, either directly or indirectly with infected poultry or fowl. This paper intends to explore the history of the flu as well as what is being done to combat this infectious and deadly disease.

Avian Influenza, also known as Avian flu or "bird flu" is "an infectious disease of birds caused by type A strains of the influenza virus" according to the World Health Organization. Identified over 100 years ago in Italy it has now spread throughout the entire globe. The immune systems of some bird species are more resistant to this disease than other although it is believed that all species are susceptible to becoming infected with the disease. The flue ranges "from mild illness to a highly contagious and rapidly fatal disease results in severe epidemics."

Facts of the Disease:

The fatal version of the disease is known to be a "highly pathogenic avian influenza."

Characteristics of this disease have been listed by the World Health Organization as being that of:

Sudden onset, severe illness, and rapid death with a near 100% mortality rate"

There are fifteen subtypes of this disease which infect birds with all of the "outbreaks" of the "highly pathogenic form" attributed to the virus influenza A of "subtypes H5 and H7." According to the World Health Organization the "live bird market as well as direct and indirect contact of domestic birds with migratory waterfowl is also connected to the epidemics." Research reveals that "viruses of low pathogenicity can...mutate into highly pathogenic viruses." The fact that influenza A viruses (this includes the subtypes) can "reassort genetic material, known as antigenic shift and merge" according to the WHO. The World Health Organization's Web site is located at http://www.who.int/csr/don/2004_01_15/en/.

History of Avian Influenza:

The first outbreak of the flu in humans occurred in 1997 in Hong Kong when 18 people were infected with the H5N1 strain and 6 of the 18 died. The outbreak was connected to human contact with "live infected poultry." Genetic studies found that the virus had "jumped directly from birds to humans." The entire poultry population in Hong Kong (1.5 million birds) is said to have averted the disaster of a pandemic. There have been other alarms of the flue with the most recent being in January 2004. The WHO states that if over time more humans become infected with the human virus strain and then "concurrently with the Avian flu that may serve as the 'mixing vessel' for emergence of a novel subtype with sufficient human genes for easy transmission from one person to another. It is believed that the flu is transmitted "primary via large respiratory droplets." Rationale given for the use of precautions is stated as being that:

The risk of serious disease and increased mortality from highly pathogenic avian influenza may be significantly higher than from infection by human influenza viruses. Each human infection represents an important opportunity for avian influenza to further adapt to humans and gain the ability to transmit more easily among people. Although rare, human-to-human transmission of avian influenza may be associated with the possible emergence of a pandemic strain."

III. Recent News and Statistics for 2004:

The Ministry of Public Health in Thailand confirmed the death of a 9-year-old girl from the northern province of Phetchabun attributed to avian influenza of the type H5N1. Symptoms developed on the 23rd of September and the girl was hospitalized four days later and died on October 3, 2004, of respiratory disease of a sever nature. The child had prepared birds for cooking after chickens died. The recommendations of WHO are for better educating the public concerning self-protection from possibly infected fowl. The reports states that:

Progress is needed on three fronts. Firstly, countries experiencing outbreaks need to rapidly share human and animal viruses with laboratories in the WHO Global Influenza Surveillance Network. Analysis of these viruses determines the possible needs for changes in the prototype vaccine "see" strains which WHO makes available to the pharmaceutical industry." Secondly, companies need to engage in research on pandemic vaccine development that includes a pilot production of small batches for clinical testing. Thirdly, public health agencies need to engage in discussion with pharmaceutical companies to explore areas of common interest in vaccine development and identify areas where support is needed."

According to the report located online at (http:www.who.iont/wer/2004/en/wer7942.pdf),WHO made the prototype seed strain for an H5N1 vaccine available to manufacturers in April 2004. However, only two of the approximate 12 companies that produce flu vaccines have moved ahead with a vaccine. Aventis Pasteur, Inc. And Chiron Corp., both of the U.S. have produced small batches to be used in clinical trials, which are not expected to take place before year's end.

IV. Measures being taken to minimize public health risks:

WHO: Reduce opportunities for human exposure to the virus, vaccination of high-risk individuals. Proper clothing and equipment against infections for those involved in the culling of poultry flocks. Workers receiving antiviral drugs as a prophylactic measure.

Testing is rapid and reliable. Antiviral drugs are effective against influenza A virus strains but have limitations, these drugs are expensive and supplies are limited. Production of influenza vaccines are considerable but as it changes years to year in composition to match the antigenic drift it takes four months to produce new vaccine in significant quantities.