Meningococcal disease spreading in Oregon State University
Meningococcal disease is caused by the bacteria called Neisseria meningitis. It is “a serious infection of the thin lining that surrounds the brain and spinal cord” (WHO). According to the World Health Organization, the fatality of this kind of disease is as high as 50% if the patient is not treated well in time. Also, it can lead to severe sequelae with a high probability of 10%. The meningococcal disease is spread through “the exchange of respiratory and throat secretions like spit” (CDC).
As mentioned in class, the spread of disease usually depends on how many people a patient get in touch with, the probability that a disease will spread from a patient to a healthy people, and how long the incubation period is.
From 2016 to 2017, a total of 5 cases of Meningococcal disease outbroke among the students at Oregon State University. And the infection often occurs in “congregate living facilities such as dorms and fraternity house” because students have more contact with each other in the dorm room, which leads to a bigger probability of spreading the disease. It is estimated that there are about 30,000 students at Oregon State University. So we can model the situation in theory like this:
(The red node stands for people who have the disease, and the edge represents the contact between people. p is the probability of infection. This graph only shows part of the network in the university.)
According to the model, the probability of infection might be as low as 0.001%. But this model is not very accurate because it is hard to tell whether it is student X spread the disease to several other students at the same time or the disease is spread one by one in the sequence as this model shows. Also, if the patient is not isolated after being infected and the probability of infection is not zero, then Ro, which is the expected number of people someone will infect, is bigger than 1, and the disease will never die out. However, luckily, after one year, the disease was finally diagnosed entirely in Oregon State University. Besides having all the patients isolated from the crowd as soon as they discovered the disease, another thing the university did was to give 19,000 OSU students vaccinated for the Meningococcal disease which might lower the probability to almost 0. This makes R0 becomes smaller than 1 so that the disease will finally die out after a finite wave.
This leads to the topic which was mentioned in the class about ways people can reduce R0 in order to prevent further spread of disease. One of them is to reduce p by increasing sanitation, like the vaccine or washing hands frequently and avoid respiratory or throat secretions contact in this situation. Another method is to reduce k by avoiding large gathering, like isolate the patient. Another example is in September, an international flight was canceled because 10 of the passengers had flu. This discourages of traveling reduce the people patients can get in touch with, especially limit the spread of the disease to another country (CNN).
WHO: http://www.who.int/news-room/fact-sheets/detail/meningococcal-meningitis
CDC: https://www.cdc.gov/meningococcal/index.html
News Article: https://www.gazettetimes.com/news/local/menb-outbreak-over-at-osu/article_dbd16d7b-bbbc-5a65-add1-cc01aa565f08.html
CNN: https://www.cnn.com/2018/09/05/health/new-york-plane-jfk-passengers-ill/index.html