Cohorted Communities and Infectious Disease
Cohorted Communities and Infectious Disease
Living in close proximity to others is a strong risk factor for the transmission of many diseases, including tuberculosis, pneumonia, and influenza. That is why infections tend to spread among cohorted communities— that is, large groups of people occupying the same living space. Individuals tend to share, or come into contact with, items which could transmit infection. The types of diseases transmitted in cohorted communities vary, depending on the characteristics of the group. However, three situations pose specific public health problems. College students living in dormitories may be more vulnerable to meningitis, an infection of the lining of the brain. People in prison, both inmates and staff, may be exposed to a number of infections, including HIV and tuberculosis. Finally, the elderly, frail residents of nursing homes run a high risk of urinary and gastrointestinal infections, as well as pneumonia.
Close contact between individuals in overcrowded dwellings has always been a factor in the transmission of disease. In modern societies, people generally have more personal space, but there are still situations when they may be at risk of infection because they find themselves in close proximity to others. In recent years, college students have become a focus for concern.
At colleges and universities, thousands of students may live together in shared residence halls or dormitories. Although most students are young and healthy, these conditions put them at risk of two infections in particular—mononucleosis (sometimes known as glandular fever) and bacterial meningitis. Mononucleosis is spread through saliva (that is why it is sometimes known as the “kissing disease”), so close physical contact between individuals and sharing items such as drinking glasses will increase the risk. Mononucleosis is characterized by sore throat, fever, and extreme fatigue; there is no cure other than prolonged rest, which will interrupt studies.
WORDS TO KNOW
COHORT: A cohort is a group of people (or any species) sharing a common characteristic. Cohorts are identified and grouped in cohort studies to determine the frequency of diseases or the kinds of disease out comes overtime.
ISOLATION AND QUARANTINE: Public health authorities rely on isolation and quarantine as two important tools among the many they use to fight disease outbreaks. Isolation is the practice of keeping a disease victim away from other people, sometimes by treating them in their homes or by the use of elaborate isolation systems in hospitals. Quarantine separates people who have been exposed to a disease but have not yet developed symptoms from the general population. Both isolation and quarantine can be entered voluntarily by patients when public health authorities request it, or it can be compelled by state governments or by the federal Centers for Disease Control and Prevention.
Bacterial meningitis, an inflammation of the meninges, which are the membranes covering the brain and spinal cord, is a far more serious condition. In students, the cause of meningitis is usually Neisseria meningitides which is present in the normal flora—or natural bacterial community—of the nose and mouth. It has long been known that meningitis is transmitted more readily among closed or crowded populations. Meningitis gives rise to high fever, severe headache, and stiff neck; it carries a mortality rate of around seven percent.
Prison inmates face a quite different spectrum of infection risk from overcrowding, with bloodborne viruses (BBVs) being the main concern. A high proportion of prison entrants have a history of drug use and so are likely to be infected with BBVs. Standards of hygiene within prison may be low, because of institutional failures combined with a lower standard of education among inmates, which encourages the spread of BBVs and also tuberculosis.
Finally, elderly residents of many nursing homes have been found to be at risk of several infections, including pneumonia, tuberculosis, diarrheal diseases; some of these infections are antibiotic resistant. Older people are more at risk of infection because they may have other chronic illnesses, and their immune systems tend to be weaker and less able to throw off an infection. Standards of hygiene may be lower in the presence of residents who are incontinent or who have dementia, thus increasing the likelihood of outbreaks of infectious disease.
IN CONTEXT: TRENDS AND STATISTICS
The Centers for Disease Control and Prevention (CDC) analyzed four studies of meningitis and concluded that American college students in dormitories, especially freshmen, had an increased risk of meningitis. Students in the United Kingdom run a similar risk. U.S. surveillance begun in 1998 suggested freshmen living in dormitories had a higher rate of meningitis (4.6 per 100,000) than any other group of the population, except for children under age two.
Research in prisons suggests that the rate of HIV infection ranges from 0.2% to over 10% and reveals case reports of transmission through sharing injecting equipment and sexual activity.
Meanwhile, research on nursing homes suggests influenza, which can be fatal in the elderly, is the most common cause of infectious outbreak. Reactivation of old tuberculosis (TB) infection is also common. Norwalk, rotavirus, and Clostridium difficile account for many outbreaks of gastrointestinal infection among nursing homes.
There are many ways in which the spread of infection in cohorted communities can be prevented. Hygiene, both personal and institutional, should be paramount, whether the setting is a college dorm, a daycare center, a prison, or a nursing home. Programs that provide condoms and syringes have been found to decrease HIV transmission among at-risk populations. Screening of potential entrants to prisons and nursing homes for relevant infections such as HIV or TB can help identify those at risk and give treatment where appropriate. The CDC also recommends that freshmen entering dorms receive vaccination against meningitis.
Cohorting is also used to prevent the spread of infection under some conditions. Physicians, especially those who specialize in treating children, often provide separate waiting areas in their offices to separate sick patients from those without symptoms. Hospitals often cohort patients with like infections into semi-private rooms. During a large-scale epidemic of infectious disease, community health officials have plans to both cohort infected persons (such as in the SARS outbreak in Singapore in 2003, where all suspected SARS cases were taken to one hospital for evaluation and care) and to suspend natural cohorting that could encourage disease spread (including temporarily closing schools).
Mandell, G.L, J.E. Bennett, and R. Dolin. Principles and Practice of Infectious Diseases. 6th Ed. Philadelphia: Elsevier, 2005.
Hellard, M.E., and C.E. Aitken. “HIV in Prison: What are the Risks and What Can Be Done?.” Sexual Health. 1 (2004): 107–113.
“Meningococcal Disease and College Students.” Morbidity and Mortality Weekly Reports. 49 (June 30, 2000): 11–20.
Strausbaugh L.J., S.R. Sukumar, and C.L. Joseph. “Infectious Disease Outbreaks in Nursing Homes: An Unappreciated Hazard for Frail Elderly Persons.” Clinical Infectious Diseases. 36 (2003): 870–876.