Modeling Infectious Disease in Humans and Animals presents more of a balance. It is an introduction to real-time and predictive modeling of infectious disease intended primarily for health care professionals, epidemiologists and evolutionary biologists. Blue book Guidelines for the control of infectious diseases. The blue book: guidelines for the control of infectious diseases has been published by the Communicable Disease Prevention and Control Unit Victorian Department of Health, to assist public health practitioners in the prevention and control of infectious diseases.
Emerging Infectious Diseases offers an introduction to emerging and reemerging infectious disease, focusing on significant illnesses found in various regions of the world. Many of these diseases strike tropical regions or developing countries with particular virulence, others are found in temperate or developed areas, and still other microbes and infections are more indiscriminate. This volume includes information on the underlying mechanisms of microbial emergence, the technology used to detect them, and the strategies available to contain them. The author describes the diseases and their causative agents that are major factors in the health of populations the world over.
The book contains up-to-date selections from infectious disease journals as well as information from the Centers for Disease Control and Prevention, the World Health Organization, MedLine Plus, and the American Society for Microbiology.
Perfect for students or those new to the field, the book contains Summary Overviews (thumbnail sketches of the basic information about the microbe and the associated disease under examination), Review Questions (testing students' knowledge of the material), and Topics for Further Discussion (encouraging a wider conversation on the implications of the disease and challenging students to think creatively to develop new solutions).
This important volume provides broad coverage of a variety of emerging infectious diseases, of which most are directly important to health practitioners in the United States.
Abstract
Prolonged human spaceflight to another planet or an asteroid will introduce unique challenges of mitigating the risk of infection. During space travel, exposure to microgravity, radiation, and stress alter human immunoregulatory responses, which can in turn impact an astronaut's ability to prevent acquisition of infectious agents or reactivation of latent infection. In addition, microgravity affects virulence, growth kinetics, and biofilm formation of potential microbial pathogens. These interactions occur in a confined space in microgravity, providing ample opportunity for heavy microbial contamination of the environment. In addition, there is the persistence of aerosolized, microbe-containing particles. Any mission involving prolonged human spaceflight must be carefully planned to minimize vulnerabilities and maximize the likelihood of success.
infection prevention, infection control, space medicine, aviation medicine, astronaut
The US National Aeronautics and Space Administration (NASA) is currently planning for prolonged human spaceflight. It is estimated that a mission to and from Mars will take a minimum of 520 days, the crew will be 360 million kilometers from Earth, there will be a 20-minute one-way communication delay from this distance [24], and there may be no way to return to Earth until the mission is completed. Clearly space travel creates a unique challenge of preventing and controlling infection. In addition to the physiologic effects of microgravity on humans, exposure to solar and cosmic radiation, the stress of being in a confined setting, and the myriad of changes observed in microorganisms in this unique environment all add to the complexity of this endeavor (Figure 1).
Variables that impact the risk of infectious diseases and their transmission during space travel.
Variables that impact the risk of infectious diseases and their transmission during space travel.
Crucian and Sams wrote, “it cannot yet be firmly concluded that a clinical risk related to immune dysregulation actually exists for exploration-class spaceflight” [1]. Nevertheless, in microgravity, potential microbial pathogens demonstrate enhanced expression of virulence factors [2–5], more rapidly enter into log-phase growth in liquid media [6, 7], and may increase biofilm formation [8]. At the same time, there is dysregulation of the human immune system during space travel, which may increase risk of infection [9–11], including reactivation of herpesviruses [12]. In addition, anaerobic colonic flora is diminished with a commensurate increase in aerobic bacteria such as Pseudomonas and Staphylococcus aureus [13, 14] and there is a greater abundance of S. aureus, along with Enterobacteriaceae, on the skin [13] and in the upper airway [14]. Numerous conditions that are conducive to the spread of infection exist within the confines of a containment vessel such as the International Space Station. Transmission of microbial flora among astronauts, including some multidrug-resistant pathogens, has been demonstrated [13, 15–20]; microbes survive in free-floating condensate [21]; and symptom-based management of medical conditions [22] may be carried out by individuals who may not have medical or nursing degrees and must confer with earthbound physicians at Mission Control. Based on postflight medical debriefs, there were 29 infectious disease incidents (ie, fever/chills [8], fungal infection [5], flu-like illness [3], urinary tract infection [4], aphthous stomatitis [3], viral gastroenteritis [2], subcutaneous skin infection [2], and other viral disease [2]) among approximately 742 crew members who have flown 106 space shuttle flights [23].
This review explores the challenges of preventing and controlling infections and suggests potential countermeasures. The opinions expressed are those of the author. It is hoped that the article will engender greater collaboration among the infection control, infectious diseases, and space science communities.
INFECTION PREVENTION CHALLENGES
The Astronaut
The immune system undergoes a number of changes during space travel [9, 10], including impaired wound healing [25], inhibition of leukocyte blastogenesis and altered leukocyte distribution [26–28], altered monocyte and granulocyte function [28–30], impaired leukocyte proliferation following activation [31], altered cytokine production patterns [26], abrogated bone marrow responsiveness to colony-stimulating factors [32, 33], altered T-cell intracellular signaling [34], inhibition of natural killer cell activity [35], inhibition of delayed-type hypersensitivity [36, 37], and apparent Th2 potential bias shift [10]. Although the effects of spaceflight on human gut flora have not been studied extensively, changes in the human microbiome have been demonstrated, with reduced density of anaerobic flora and increased density of aerobic gram-negative bacteria and staphylococci on the skin and in the upper airway and colon [14]. Additionally, stress associated with space travel in a confined environment may induce changes in the intestinal microbiome that are unrelated to microgravity, and this may impact immune function [38, 39].
The Microbe
In microgravity, bacteria demonstrate enhanced growth patterns in liquid media [6], reflecting a shortened lag phase and enhanced exponential growth [7]. Additionally, bacteria demonstrate enhanced virulence [2–5]; higher minimal inhibitory concentrations to various classes of antimicrobial agents [40–42], which is at least partly due to thickening of the microbial cell wall [43, 44]; increased conjugal transfer rates [45]; increased production of quorum-sensing molecules such as N-acyl homoserine lactone [46]; enhanced virulence, leading to increased mortality in animal infection models [47]; increased biofilm formation [48]; and increased survival within macrophage [4]. For additional information on the effect of microgravity on microbes, see Horneck et al [49].
The Spacecraft or Space Habitat
The internal environment of a spacecraft or space station can become heavily contaminated with microbes [50], and free-floating condensate has been found to harbor numerous bacteria, fungi, and even protozoa [21]. Microgravity affects the aerobiology of the aerosols that are created from a cough or sneeze or during speech. Particles remain airborne until they are inspired, swallowed, contact an otherwise absorbable surface, or are ideally promptly removed by an air filtration system. The presence of these aerosols affects the risk of person-to-person transmission of viruses such as influenza [51–53] and even bacteria such as S. aureus [54, 55].
PREFLIGHT COUNTERMEASURES
Interventions for mitigating the risk of infection prior to space travel are described in this section (Table 1).
Preflight Countermeasures
• Medical/dental history and physical | ||
• Vaccination
|
|
|
• Screening, decolonization, and treatment if colonized or infected, respectively ○ Tuberculosis (interferon-gamma release assay) ○ S. aureus (screen nares for MRSA) ○ Human immunodeficiency virus (serology) | ○ S. aureus (screen multiple body sites for MRSA and MSSA) ○ Salmonella (screen multiple stools) ○ Strongyloides (serology) ○ Endemic fungi (serology for coccidiomycosis; histoplasmosis) |
|
• Isolation from community for a period of time equal to the incubation period for viral respiratory and gastrointestinal pathogens and bacterial pathogens that cause food poisoning | • Infection control education (eg, hand hygiene, cough etiquette) | |
• Training for aseptic insertion of intravenous and bladder catheters | ||
Animals
|
| |
Plants • Nonsoil-based growth | ||
Containment vessel
|
| Reverse osmosis for potable water
|
Other
|
• Medical/dental history and physical | ||
• Vaccination
|
|
|
• Screening, decolonization, and treatment if colonized or infected, respectively ○ Tuberculosis (interferon-gamma release assay) ○ S. aureus (screen nares for MRSA) ○ Human immunodeficiency virus (serology) | ○ S. aureus (screen multiple body sites for MRSA and MSSA) ○ Salmonella (screen multiple stools) ○ Strongyloides (serology) ○ Endemic fungi (serology for coccidiomycosis; histoplasmosis) |
|
• Isolation from community for a period of time equal to the incubation period for viral respiratory and gastrointestinal pathogens and bacterial pathogens that cause food poisoning | • Infection control education (eg, hand hygiene, cough etiquette) | |
• Training for aseptic insertion of intravenous and bladder catheters | ||
Animals
|
| |
Plants • Nonsoil-based growth | ||
Containment vessel
|
| Reverse osmosis for potable water
|
Other
|
Abbreviation: Esp, extracellular serine protease; MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-susceptible Staphylococcus aureus.
Preflight Countermeasures
• Medical/dental history and physical | ||
• Vaccination
|
|
|
• Screening, decolonization, and treatment if colonized or infected, respectively ○ Tuberculosis (interferon-gamma release assay) ○ S. aureus (screen nares for MRSA) ○ Human immunodeficiency virus (serology) | ○ S. aureus (screen multiple body sites for MRSA and MSSA) ○ Salmonella (screen multiple stools) ○ Strongyloides (serology) ○ Endemic fungi (serology for coccidiomycosis; histoplasmosis) |
|
• Isolation from community for a period of time equal to the incubation period for viral respiratory and gastrointestinal pathogens and bacterial pathogens that cause food poisoning | • Infection control education (eg, hand hygiene, cough etiquette) | |
• Training for aseptic insertion of intravenous and bladder catheters | ||
Animals
|
| |
Plants • Nonsoil-based growth | ||
Containment vessel
|
| Reverse osmosis for potable water
|
Other
|
• Medical/dental history and physical | ||
• Vaccination
|
|
|
• Screening, decolonization, and treatment if colonized or infected, respectively ○ Tuberculosis (interferon-gamma release assay) ○ S. aureus (screen nares for MRSA) ○ Human immunodeficiency virus (serology) | ○ S. aureus (screen multiple body sites for MRSA and MSSA) ○ Salmonella (screen multiple stools) ○ Strongyloides (serology) ○ Endemic fungi (serology for coccidiomycosis; histoplasmosis) |
|
• Isolation from community for a period of time equal to the incubation period for viral respiratory and gastrointestinal pathogens and bacterial pathogens that cause food poisoning | • Infection control education (eg, hand hygiene, cough etiquette) | |
• Training for aseptic insertion of intravenous and bladder catheters | ||
Animals
|
| |
Plants • Nonsoil-based growth | ||
Containment vessel
|
| Reverse osmosis for potable water
|
Other
|
Abbreviation: Esp, extracellular serine protease; MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-susceptible Staphylococcus aureus.
The Astronaut
A robust vaccination program that includes tetanus/diphtheria/acellular pertussis (Tdap), measles/mumps/rubella (MMR), influenza, pneumococcal, meningococcal, and hepatitis A and B vaccines should be implemented. Because of increased reactivation of herpesviruses, which has been noted in past space missions [12], varicella zoster virus vaccine should be given. In the unlikely event that an astronaut is unknowingly carrying Salmonella, typhoid vaccine should be considered to reduce the 2risk of transmission.
Countermeasures during Spaceflight