Mononucleosis is a lymphatic system disease, usually caused by the Epstein-Barr virus (EBV) (first cultured by Michael Epstein and Yvonne Barr). A similar condition is often caused by the cytomegalovirus (CMV), which is also a herpes virus. Both EBV and CMV have a tendency to become latent in host cells. Incubation periods are often lengthy (4-8 weeks). Symptoms include extreme fatigue, sore throat, high fever, weight loss, and often pharyngeal inflammation. Symptoms usually persist for 2-3 weeks, occasionally even longer.
Fatigue symptoms often persist even longer. Infections are often likely to be permanent, but is almost never fatal. Some estimates place the incidence of infection as high as 90% of the worlds population. After the initial infection period, generally the virus causes no noticeable symptoms, although the age of the infected individual does seem to matter. During the teen years, more symptomatic disease results than does an infection occurring either before or after this time. A big factor in the virulence of this disease is its long incubation and latency periods.
Link 2: Reservoir (10 pts) [Fill in where it normally lives, or its normal host. ] Humans are the main hosts for mononucleosis. After symptoms have subsided, EBV cells may reside in the host’s throat and blood permanently. These people are periodically able to spread the disease for the duration of their lives, often without exhibiting any symptoms of the ailment themselves. This, of course makes the transmission of the disease almost impossible to prevent. Link 3: Portal of Exit (5 pts) [How does it exit the reservoir?
Does it use a vector? If the reservoir is a person, how does it leave the body? ] The virus leaves the body through the direct contact with the saliva of an infected person. Mouth-to-mouth kissing is the most likely means of viral infection. Transmission through blood transfusion, sexual contact, or organ transplantation is possible, but much less likely. Infection via inhalation has not normally been known to occur. Link 4: Mode of Transmission (10 pts) [Fill in how it is transmitted to humans and between humans.]
Transmission of mononucleosis is normally through kissing or other direct mouth-to-mouth contact with the saliva of an infected person. Other means of transmission may have occurred, but seem to be statistically insignificant. Usually when a person has previously been exposed to the disease, they are not at risk of re-infection. The prevalence of the ailment makes it impractical to implement any isolation or special preventive measures because many healthy people are latent, sometimes long-term carriers of EBV.
Once infected, individuals are able to transmit the disease initially for a few weeks. Long-term latency with periods of symptomless re-activation bring forth episodic periods of communicability in infected individuals, often for their entire lifetime. Link 5: Portal of Entry (5 pts) [How does it enter the human body? ] Mononucleosis enters the body the same way it leaves it, normally with the exact same activity, namely mouth to mouth kissing, human mouth to human mouth. Other means of entry have been noted, but are very rare occurrences. Link 6: Susceptible Hosts (10 pts).
[Who contracts this disease? Who are the most most vulnerable populations? ] The ubiquitous, universal transmittal of mononucleosis makes most of the worlds population the carriers and transmitters of this disease, often for very long periods of their lives. The disease in its symptomatic, observable form is normally more likely seen in the developed world, as opposed to other parts of the world due to the fact that in underdeveloped parts of the world children are exposed to the disease at an earlier age, usually exhibiting few if any notable symptoms.
The most vulnerable are teens and young adults who may have more kissing partners due to their unattached situation in life and are more likely to be exposed to the infection. Epidemics are normally associated with outbreaks of normally contained and controlled pathogens.
Due to the wide spread nature of mononucleosis it would be very difficult to contain or control this disease. Fortunately, this is not a deadly disease and its symptoms normally exist for a relatively short period of time. Therefore, many of the consequences of what would be known as an epidemic or pandemic would be mitigated due to the relatively mild and nonfatal results of infection.
References: National Center for Infectious Disease. CDC Epstein-Barr Virus & Infectious Mononucleosis. Updated June 16,2006 from http://www. cdc. gov/ncidod/diseases/ebv. htm Cowan, M. K. & Talaro, K. P. (2009) Microbiology A systems Approach (Second Edition) NY, NY McGraw-Hill.