EUGLOREH project




10.3. Physical environment factors

10.3.3. Biological agents

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10.3.3. Biological agents





European Centre for Diseases Control


Methicillin-Resistant Staphylococcus Aureus


Haemophilus influenzae type b


Variant Creutzfeldt-Jakob disease Introduction


Biological hazards include viruses, bacteria and fungi and more recently discovered agents such as prions; often, they are ubiquitous and can all pose serious risks to public health, particularly in combination with the growing impact of antimicrobial resistance. Biological stressors are responsible for the occurrence of a variety of communicable diseases. Of the 49 diseases under surveillance by the European Centre for Diseases Control (ECDC), 21 have incidence levels that are in double or triple digits per million population with half of these 21 also having rising (or steady) trends. The fact that three of the six communicable diseases with the highest incidence in the EU belong to this group, and include the two diseases with the highest crude incidence rates in the EU (Chlamydia infection and Campylobacteriosis) which could in part be due to improved surveillance represents a great concern. In 22 diseases, the age groups most affected were under 24 years of age, indicating that more action is needed to protect the health of our future generations. Of the main disease groups, the ‘Zoonoses’ and ‘Serious imported diseasegroups had the lowest incidence rates and also show decreasing trends (except for avian influenza and malaria). Every year approximately three million people in the European Union catch a healthcare-associated infection and approximately 50 000 of these people die as a consequence. The most important communicable disease threat in Europe is posed by the increasing number of micro-organisms strains that have become resistant to antibiotics. Data sources


See Chapter 6. Data presentation and analysis


Antimicrobial resistance (AMR)


The bacterium that has received prime attention is methicillin-resistant Staphylococcus aureus (MRSA). A larger and larger proportion of all invasive S. aureus infections is caused by MRSA. Evidence from the countries participating in the EU-funded EARSS surveillance program, including countries with high, medium and low baseline figures, shows that a general increase in MRSA is occurring throughout Europe (Figure However, two countries (Slovenia and France) have succeeded at significantly reducing the proportion of , thus demonstrating that this MRSA pandemic may not be irreversible.


Figure Proportion of MRSA isolates in 2005 in Countries participating to EARSS project




For most other bacteria under EU surveillance the overall trend is also very worrying, with AMR is a particular concern when it comes to the global killer diseases TB, malaria, HIV and pneumococcal infections. Resistance has also evolved against viral (e.g. HIV, influenza), parasitic (malaria) and fungal infections, making AMR the most serious of all threats associated with communicable disease.




Viruses are among the most dangerous biological agents for human health. Seasonal influenza is an acute viral disease of the respiratory tract, caused by influenza virus A and B; each year there are epidemics during the winter season, although sporadic cases do occur throughout the year; seasonal influenza poses a considerable public health threat. SARS is a viral respiratory illness with a high fatality rate, caused by a corona virus, the SARS-associated corona virus (SARS-CoV); the main way that SARS seems to spread is by close person-to-person contact, through respiratory droplets produced when an infected person coughs or sneezes. Human immunodeficiency virus (HIV) is a retrovirus, which attacks the immune system and may lead to severe illness following a long incubation period. The end-stage of the infection, acquired immunodeficiency syndrome (AIDS), results from the destruction of the immune system. Measles is an acute illness causes by morbillivirus. Mumps is caused by the mumps virus. Rubella is a mild febrile rash illness affecting both adults and children. The most serious consequence of rubella results from infection during the first trimester of pregnancy, when rubella infection can cause miscarriage, foetal death or severe birth defects. Polio is caused by poliovirus, which infects the gastrointestinal tract and spreads to regional lymph nodes, but can also spread to the central nervous system. In recent years, a new strain of avian influenza (A/H5N1) has spread globally among birds, and also occasionally infected humans. The threat of avian influenza and its potential for starting a human influenza pandemic is a main concern. Hepatitis A is declining in Europe, but this also means that more and more people remain susceptible to this virus and smaller outbreaks are still seen in several countries. An effective vaccine is available but it is recommended mostly for travellers. Norovirus and rotavirus infections are not reportable in the EU, but are both important causes of gastroenteritis all over the Union. It may be that outbreaks caused by norovirus in confined places, such as schools, hospitals and cruise ships are on the increase, but it should be noted that methods for laboratory diagnosis have really been available only in the last decade.




Bacteria may also have very dangerous biological stressors. Tubercolosis is a bacterial disease, which affects the lungs as well as many other organs; it is most commonly acquired via inhalation of bacteria belonging to the Mycobacterium tuberculosis complex in droplets produced by another person with pulmonary disease, and less frequently through ingestion of contaminated milk or through laboratory contamination. Legionnairesdisease is a respiratory disease caused by the bacteria Legionella pneumophila, which can give severe pneumonia with high case fatality rates, especially among elderly and immuno-compromised individuals. Streptococcus pneumoniae (pneumococcus) mainly affects the youngest and oldest individuals, and is the main cause of bacterial respiratory tract infections in all age groups. Invasive meningococcal disease, caused by the bacterium Neisseria meningitides (meningococcus), is most common in young children, with a secondary peak in disease incidence among teenagers. Haemophilus influenzae type b (Hib) is a respiratory tract bacterium, capable of causing meningitis and other severe systemic infections in young children. Pertussis is an acute bacterial infection of the respiratory tract caused by the Bordetella pertussis bacterium. The disease is characterised by an irritating cough that may last up to two months or even longer. Diphtheria is an acute disease with inflammation of the mucosal surfaces of the upper respiratory tract caused by a toxin from the Corynebacterium diphtheriae bacterium. Tetanus is induced by an exotoxin of the Clostridium tetani bacterium. Two important food-born or water-borne infections, salmonellosis (including typhi and paratyphi) and shigellosis, seems to be on a declining trend in the EU. Campylobacter is the most commonly diagnosed food-borne bacteria in the EU, and may be slightly increasing over time, while Cryptosporidium has caused waterborne outbreaks in several Member States. Although the majority of the symptomatic Campylobacter and Salmonella infections do not require any drug treatment, invasive infections do occur. Zoonoses are diseases or infections, which are transmissible from animals to humans. The infection can be acquired directly from animals or through the ingestion of contaminated foodstuff. In humans, the gravity of these diseases can vary from mild symptoms to life threatening conditions. The importance of a zoonosis as a human disease depends on several factors, such as the severity of the disease, the case fatality and number of cases (incidence) in the population.




Parasites are other well known biological stressors. Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii. The infection is asymptomatic in most humans, but can be life-threatening in immuno-compromised individuals. Giardiasis is a parasitic infection caused by Giardia intestinalis, causing both acute and chronic diarrhoea. Infants and children are at particular risk. Cryptosporidiosis is a parasitic disease caused by Cryptosporidium, infecting many species of large and small animals. The parasite can cause profuse and watery diarrhoea; humans can be infected from other people or from the environment. Echinococcosis is a zoonotic parasitic disease, caused by the larval stage of the tapeworm Echinococcus. Humans are infected through close contact with infected animals (sheep, cattle, goats, horses, pigs) or through ingestion of undercooked infected food. Trichinellosis is a zoonotic disease caused by Trichinella. The first symptoms are diarrhoea and abdominal cramps, but following larval invasion to the muscles, muscular pain and fever become characteristic symptoms.




Variant Creutzfeldt-Jakob disease (vCJD) is a novel form of human spongiform encephalopathy (prion disease). The clinical picture is characterised by psychiatric symptoms followed by progressive neurological deterioration. The disease is fatal, with a mean survival of about 14 months. The main suspected route of transmission is through past consumption of infected beef products, although recently human-to-human transmission has been described through blood transfusion. Preventive measures include ensuring that the BSE prions, mainly localized in the brain and other parts of the nervous system of infected cattle, do not enter the human or animal food chains, and that blood or tissue for transplants from potentially infected persons are not used in medical care.

BSE prion was found to be highly resistant to thermal inactivation and to digestion in the gastro-enteric tract.


Impact on health of specific biological hazards


For some diseases there has been a significant reduction in the incidence and number of cases through concerted prevention and control action by Member States (even though levels remain high in specific population segments and risk groups) (table


Table Summary of general trends (19952005), main age groups affected (2005), and major threats detected (2005) for diseases reported on EU-level Control tools and policies


See Chapter 6. Future developments


See Chapter 6. References


See Chapter 6.