Rabies is a viral disease that is usually spread to humans by contact with infected animals.  The virus waits in the salivary glands of the animal.  Once they bite someone, it travels into the broken skin and into the brain tissue where it wreaks havoc.

According to the Center for Disease Control (CDC, 2011), in the last 100 years there has been a change in the types of animals causing the most rabies transmission in the United States.  Although the most common culprits worldwide are domestic animals such as dogs, especially in under-developed countries, in the United States the most common hosts are “wild carnivores and bats”.  Wild carnivores include raccoons, foxes, coyotes and skunks (CDC, 2011).  This change of host is likely due to the rabies vaccines that are administered to domestic animals on their routine veterinarian visits, which began in the 1940s (Finnegan, C. J., S. M. Brookes et al., 2003).

Since the 1900s, rabies mortality in the United States has decreased from approximately 100 fatalities annually to about one or two (World Health Organization [WHO], 2017).  This is largely due to routine vaccination of domestic animals.  In addition, the majority of the population in the United States has easy access to health care and post-exposure prophylaxis is readily available (CDC, 2011).  The United States population is also well informed, and has access to a variety of resources that would allow them to research the risks of being bitten by an animal, especially a wild animal such as a bat, raccoon, bat, skunk, fox, coyote and domestic pets as well.

These are all things that may not be as accessible to the rest of the world, which is a likely reason why most deaths due to rabies occur in areas with less than adequate health care in combination with living in an area that does not vaccinate domestic animals, and has no access to internet or other resources to keep educated on a topic unless provided to them.  This limitation of awareness was found in Thailand, where although knowledge about rabies and its severity are high, “awareness about bat transmission specifically was very low”.  In fact, only 10% of the people who took a survey identified bats as a potential source of rabies, and 36% said they would likely not take any specific action if bitten by a bat (Robertson, Kis, Boonlert Lumlertdacha, et. al., 2011).  According to the WHO, although all continents are affected by rabies, 95% of deaths occur in Asia and Africa.  Even if rabies post-exposure prophylaxis (PEP) is readily available to the people in these areas, the costs of PEP are $40 and $49 respectively (WHO, 2017).  A cost that even some uninsured American citizens may have difficulty paying; let alone a person in Asia or Africa whose “average daily income can be between $1-2 per person” (WHO, 2017).

Furthermore, the diagnosis of rabies has also evolved.  Previously, rabies was a post-mortem diagnoses in animals.  Meaning that the animal, if not dead already, had to be euthanized in order to take brain samples and confirm the diagnosis (CDC, 2011). Today, instead of euthanizing a perfectly healthy animal, the animal can be watched for 10 days after it bites someone and if no symptoms of rabies appear, the animal is said to be rabies free (CDC, 2011).  This not only decreases harm to healthy animals, but also reduces the need to treat prophylactically, which according to the WHO is high, “typically exceeding 3,000” (WHO, 2017). Diagnosing rabies in humans is quite different, and although there are many diagnostic tests available, the WHO reports that those available are not “suitable for detecting rabies infection before onset of clinical disease”.

The “Fatal Infestations”, video about the rabies outbreak was devastating, especially because of the fact that rabies is a preventable and curable disease if caught before symptoms of the infection emerge.  Since rabies is an infection of the nervous system, symptoms include seizures, erratic behavior and aggression, excessive salivation (drooling), aversion to water (hydrophobia) and even paralysis, and coma.  Once any of these symptoms manifest, the disease is too far-gone and recovery is unlikely (CDC, 2011).   Although the symptoms of rabies are likely to be well known by physicians, many times the diagnoses is missed. In the medical field there is a common saying, “If you don’t think of it, you will not diagnose it,” and in this case rabies was not thought of as a possibility just as the video proposed.

An epidemiological investigation requires certain steps to be taken in whichever order the investigator deems necessary (Gregg, Michael B, 3-13).  The video shown in class showed a small portion of what an actual investigation entails.  The investigation began when the CDC was called by local health departments because of concerns of an outbreak.  The video shows the CDC arriving and speaking with the families acquiring what is called descriptive epidemiology: when, where, who, how many (Gregg, Michael B, 156-157).  They looked for connections between all three victims now in a coma, intubated and in the ICU.  They then conducted a series of lab tests and imaging on all patients in order to diagnose the cause, but their efforts were unsuccessful and a diagnosis could not be made. 

When the first fatality occurred, and the organ donor was identified as the source, descriptive epidemiology was continued, now centered on the donor himself. The CDC went to the patient’s home and spoke to friends and family. Luckily, this led to information about a bat bite on the donor’s chest in the previous weeks.  The CDC then requested an autopsy and sent investigators to the donor’s home looking for the bats with infrared lenses.  Multiple bats were found and taken into the CDC where they were tested for the rabies virus. The same rabies virus was confirmed to be present in both donor and bat, and source of the infection found (“Fatal Infestations”).  The video ends with the death of the last living victim.

Any situation where an individual is still alive and on the brink of death due to an unknown cause, which has already killed others, involvement of local health departments and the CDC is crucial to determine the cause and source to treat and prevent further spread. Any initial investigation requires a case count and case definition (Gregg, Michael B, 157).  In this situation, the case definition would have been:  erratic behavior, seizures and coma.  The count would have been three with the first victim as patient zero.   The video revealed that the symptoms began approximately 3 -7 days after the organ transplant surgery meaning that whatever the cause, its symptoms occur rapidly and effects catastrophic.  This would add pressure on me as an investigator to conduct my work not only accurately, but also very quickly (Gregg, Michael B, 10-13).

My next step would be to begin data collection. Descriptive epidemiology: Demographics, exposures, similarities between all three cases, hospital information and discussions with the doctors to determine if the infection was from the surgical room, the tools used, the staff present etc. Since it is unknown whether or not any of these things are the source, I would be concerned about a larger range of exposure, and possible epidemic.

This information helps form a hypothesis of the possible source of infection and diagnosis; it would also help me decide whether or not to launch a full investigation (Gregg, Michael B, 186).  In this case I would because of the high risk of an epidemic of an unknown disease that can kill within 3-7 days. Once the organ recipient hospital can be ruled out as the source of infection, my hypothesis would turn to the donor hospital and donor himself as the possible sources.  I would use visual aids and maps to help graph the case count to orient them in place (Gregg, Michael B, 191-196).  This will help as I gather information from the donor hospital.  Doing this may show the point of origin of an infection and narrow down the possible source.  This shows that as an investigation progresses, a hypothesis will also change and become narrower until the true source is found.

The information I would require about the donor include: symptoms of the donor on arrival to the hospital, which included: erratic behavior, seizures and drooling.  Information gathered from friends and family on recent exposures, which would reveal the bat bite weeks back.  The combination of the bat bite and the symptoms, the doctor in me would immediately me concerned about rabies.  Just as the CDC did, I would request an immediate biopsy of the donor looking specifically for negri bodies in the brain (CDC, 2011), as well as send investigators to the home to look for bats.  Once the diagnosis of rabies is confirmed, there is not much that can be done for the surviving victim who received an organ from the infected donor.  Unfortunately they already presented with symptoms, and as mentioned previously, recovery is not likely.

Rabies is a viral disease that is usually spread to humans by contact with infected animals.

Now, although the video did not discuss what happened after the surviving victim passed away, it is important to know that any epidemiological investigation does not end there.  It is imperative to continue assessing risks of exposure to other people besides the initial victims.  Knowing that the latency between exposure to rabies and symptom manifestation of rabies is between 1 week and 3 months, it is essential to determine whether exchange of bodily fluids between the donor and any family and friends occurred (CDC, 2011).  If transmission of rabies is likely, PEP should be administered especially if they have not presented with neurological symptoms and in this way prevent more casualties.  Furthermore, I would be concerned about the presence of bats in the neighboring areas of the donors’ home.  If his home had bats, it is also likely that there are bats in other homes, which would place its inhabitants at risk of acquiring rabies if bitten.

A very important step in an epidemiological investigation is the formation of a written report outlining the findings, and recommendations (Gregg, Michael B, 3-13, 73-76).  Even more important is the execution of the recommendations as well as implementation of prevention measures to keep healthy people healthy and risk free of the disease.  This includes surveillance for bat, wild carnivore and rabid dog sightings.  Bats and rabid animals may infect other domestic animals, and therefore surveillance of changes in domestic animal behavior should be conducted as well.  I would thus release educational pamphlets to the population, alerting them of the possible risk of rabies if bitten by these animals and instructions on what to do if bitten such as: 1) Immediately irrigate with soap and water; as the virus is transmitted by the saliva of the animal.  2) Make an appointment with their doctor and be evaluated for possible risk of exposure and if needed receipt of PEP.  To aid in reducing rabies infected animals from the streets I would ask for assistance from Animal Control to retrieve any raccoons, bats and other possible reservoirs from the streets.

The above, includes what I would do if I were the investigator on the rabies case. 

As explained, I would do some things different from what was seen in the video.  Because of my medical background I believe I may have been able to detect the possibility of rabies sooner and avoid the delay on diagnosing.  I would have also used visual aids to help identity the common area of exposure, and the pattern of transmission.  Although in this situation the investigation took place in the United States, certain risk factors were more important than others, such as bats versus domestic animals.  If the investigation had taken place on an international level there would no doubt be different obstacles to overcome such as: language barrier, culture differences and political issues.  These would cause significant delays in acquiring data and arriving at a diagnosis quickly.  More over, certain places of the world do not trust the western world and this would affect the swift formation of hypothesis by precluding data collection, as well as the formation of prevention and treatment plans to contain the infection.

My focus, in an international setting, would be less on wild animals and more on domestic animals, which rarely get rabies vaccines and the most common causes of rabies outside of United States (WHO, 2017). The plan would include vaccinating as many dogs as possible with the aid of veterinarians both local and international, watching street dogs for signs of rabies and putting them down if confirmed.  Teaching the population about ways to protect themselves and others.  Inform families that those most at risk of acquiring rabies are their children (Finnegan, C. J., S. M. Brookes et al., 2003). It is important to educate the populations about all the likely reservoirs to avoid the issues mentioned earlier which were faced in Thailand. Preventing re-emergence and epidemics of a disease is the goal.  To do this, prevention measures are implemented. Certainly there will be issues bringing in the number of rabies vaccines needed for all the dogs, and not every risk of exposure can be prevented.  Another thing to consider is access to health care.  If someone is indeed bitten, do they know where to go to get PEP. Can they get there quickly and safely?  Will it be affordable?  All of these are obstacles that must be addressed, especially in an international setting where health care access may be vastly limited and so arriving with a plan in mind is crucial.  Overall the investigation conducted during the rabies video does show the typical course of an epidemiological investigation. I do think there were some time delays in reporting the issue to the CDC, and diagnosing the donor with rabies but fortunately the disease had only been transmitted to the three victims.   It is important to keep people as well as practicing physicians informed about rabies, its hosts, transmissions, treatment options and prognosis.



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