Zoonoses

Fact sheet

Key facts

• Over 200 zoonoses have been described, and they may be classified according to the type of causative agent, such as bacteria, viruses, parasites, fungi, or other communicable agent.
• These diseases represent significant public health threats, and although most of them can be prevented, many are not prioritized by health systems at national and international levels and are termed "neglected" diseases.
• The greatest risk for zoonotic disease transmission occurs at the human-animal interface, through direct or indirect human exposure to animals, their products and/or their environments.
• These diseases can be transmitted directly by contact with an animal (e.g., rabies, through a bite), via a contaminated environment (e.g., anthrax) and via food (e.g., campylobacteriosis), or indirectly via vectors, such as mosquitoes or ticks (e.g., West Nile fever, dengue, malaria and Lyme disease, respectively).
• Both domestic and wild animals act as reservoirs for these pathogens. The diseases they cause in humans range from mild and self-limiting (e.g., most cases of campylobacteriosis) to fatal (e.g., Ebola and rabies).
• Zoonoses are of increasing concern for human health. Approximately 60% of all human diseases are thought to be of zoonotic origin, and up to 75% of newly emerging infectious diseases may be of zoonotic origin.
• Many of the zoonotic agents causing disease in humans cause little or no obvious clinical disease in their animal hosts, suggesting that as yet unidentified zoonotic diseases may exist that pose a risk to human health.
• Examples of emerging zoonotic diseases in the past few decades include avian influenza A/H5N1, West Nile fever, Ebola, severe acute respiratory syndrome (SARS), and pandemic influenza A/H1N1 2009.
• In addition, a number of well known and preventable zoonoses continue to occur in many countries, especially in the developing world, where they mostly affect the poorest people.
• The emergence of zoonotic disease is complex and multifactorial, driven by factors that include evolving ecology, microbial adaptation, human demographics and behaviour, international travel and trade, agricultural practices, technology and industry.
• In addition to being a public health problem, many of the major zoonotic diseases prevent the efficient production of food of animal origin and create obstacles to international trade in animal products.
• Addressing zoonotic risk requires multisectoral cooperation and strong partnerships between human and animal surveillance and response systems.

The situation

• Viet Nam is one of the countries identified as a "hotspot" for zoonotic emerging infectious diseases, including those with pandemic potential.
• In 2003, Southeast Asia’s unique combination of strong links with other Asian countries, together with its global connections, facilitated the regional and global spread of the causative agent of severe acute respiratory syndrome (SARS) – the SARS coronavirus. Guests infected in a hotel in Hong Kong unknowingly carried the virus to several countries, including Viet Nam. SARS resulted in 40 cases and one death being reported to WHO from Viet Nam.

Avian influenza

• In the same year that SARS was spreading through Southeast Asia, the region began to experience outbreaks of another zoonotic emerging infectious disease, avian influenza A/H5N1, commonly called “bird flu”.
• Viet Nam was among the first countries to report cases of Highly Pathogenic Avian Influenza (HPAI) in poultry, and has been one of the countries hardest hit by avian influenza.
• The disease has resulted in significant social and economic costs, particularly among Viet Nam’s millions of household farms. This impact has been unevenly distributed, since income from poultry and eggs is more important among the poorest segments of the population.
• From December 2003, when the first human case was detected, until 2 April 2010, Viet Nam reported the second-highest number of human infections (after Indonesia), with 119 confirmed cases, including 59 deaths (50% fatality).
• Although the virus continues to circulate, causing outbreaks in poultry, Viet Nam had not reported any cases or deaths after April 2010 and up to January 2012. However, four cases and two deaths were reported in early 2012.
• Overall, up to July 2012, Viet Nam has reported 123 human cases of avian influenza and 61 deaths to WHO.

H1N1

• In 2009, cases of a novel strain of an influenza virus were identified, first in Mexico and then North America, before rapidly spreading to other parts of the world, resulting in the first influenza pandemic of the 21st century.
• This virus was a unique combination of influenza virus genes never previously identified in either animals or people. The virus genes appeared to have resulted when a previous triple reassortment of bird, swine and human influenza viruses further combined with a Eurasian swine-origin H1N1 influenza virus, leading to the term "swine flu" being the initial term used for this pandemic.
• By 10 February 2010, the Viet Namese Ministry of Health had received reports of 11,186 laboratory-confirmed cases, including 58 deaths.
• On 10 August 2012, the Director General of the World Health Organization, officially declared over that the H1N1 influenza pandemic was over and that the world had entered the "post-pandemic" phase, where virus activity would be that at levels usually seen for seasonal influenza.

Other threats

• While many zoonotic diseases may not pose a threat to global health security, they significantly impact on the health and livelihood of rural poor communities in Viet Nam. The most important of these diseases include rabies; streptcoccus suis; foodborne diseases; anthrax and leptospirosis.

WHO's response

WHO continuously supports Viet Nam in a number of areas related to zoonosis, including:

• Assessment of national capacities, gaps and needs;
• Building capacity through training courses for health staff in zoonotic disease epidemiology, preparedness; risk communication; surveillance, risk assessment and outbreak response;
• Encouraging the continuous upgrade of skills, knowledge and tools to support rapid and accurate laboratory diagnosis;
• Establishing standards for infection control practices, including laboratory biosafety;
• Supporting practical interventions to reduce the burden of disease, such as the development and dissemination of information to vulnerable groups at community level;
• Supporting the development of zoonotic disease control strategies and programmes, including the monitoring and evaluation of activities;
• Developing a mechanism to strengthen networking and a joint response to events between public health and animal health sectors;
• Advocating political commitment, information sharing, and multisectoral collaboration;
• Enhancing national capacity and research skills and promoting research to support policy development.

Effective communication and coordination between human and animal health sectors are recognised as essential for preventing and controlling zoonotic disease. Globally, WHO, in collaboration with the FAO (Food and Agricultural Organization of the United Nations) and OIE (World Organization for Animal Health), has developed guidelines for intersectoral activities.

In Viet Nam, WHO is working with the Ministry of Health and the Ministry of Agriculture and Rural Development of Viet Nam, the FAO and key stakeholders to facilitate intersectoral collaboration.

Implementation of the revised International Health Regulations (IHR 2005) began in June 2007. These regulations facilitate the strengthening of the national capacity of countries to contain the spread of emerging infectious diseases, both nationally and globally.

As a result of the need to implement the IHR, a regional strategy, the Asia Pacific Strategy for Emerging Diseases (APSED), was developed to provide a strategic framework to support strengthening of the generic capacity of countries in the control and prevention of emerging and re-emerging diseases. Control and prevention of zoonotic diseases is a key component of APSED.

While focusing on avian influenza, the priority zoonotic disease in Viet Nam, WHO is also providing technical advice and support for other zoonotic diseases such as rabies, anthrax and streptococcus suis.