Rabies

Rabies, classified as a neglected tropical disease (NTD), predominantly affects marginalized populations and underserved populations. It is a highly fatal viral zoonosis caused by the Rabies virus, a member of the Lyssavirus genus. The virus primarily targets the central nervous system, leading to inflammation of the brain, which is almost always fatal once clinical symptoms appear. Worldwide, rabies results in approximately 59,000 human deaths annually, mostly in Asia and Africa, where domestic dogs are the primary transmitter of the virus. Rabies remains a significant public health concern despite the availability of very effective vaccines, particularly in underserved areas and areas with poor health resources and facilities. The disease is 100% vaccine-preventable through timely post-exposure prophylaxis (PEP).

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation. 

The control of rabies amongst humans is highly dependent on the elimination of the virus in dogs, the primary transmitters. The following include case definitions for human surveillance and exclude case definitions for veterinary surveillance. For more information on veterinary surveillance or clinical presentations, please visit WOAH’s page on Rabies.  

Clinical description: The prodromal phase is characterised by non-specific symptoms such as fever, headache, and paresthesia (an unusual skin sensation – tingling, burning, numbness, or a ‘’pins and needles’’ feeling) at the exposure site. Rabies manifests in two clinical forms:  

• Furious (Encephalitic) Rabies: This is the more common form, involving hyperactivity, hydrophobia (difficulty and fear of swallowing water), aerophobia (fear or discomfort caused by air), and convulsions. Patients may also exhibit periods of hyperexcitability interspersed with calm, and in the terminal stages, experience cardiorespiratory arrest.
• Paralytic (Dumb) Rabies: This form accounts for about 20% of cases, characterised by gradual paralysis that begins at the site of the bite, leading to coma and death. Paralytic rabies is often misdiagnosed, leading to underreporting. 

Suspected case: A case presenting with an acute neurological syndrome (e.g., encephalitis) characterised by inexplicable hyperactivity, aerophobia, or hydrophobia, and a history of contact with a suspect rabid dog. 

Probable case: A probable case is a suspected case with a supportive history of exposure (in non-vaccinated individuals). 

Confirmed case: A suspected case that is laboratory-confirmed. 

Source of information: https://www.hpsc.ie/a-z/zoonotic/rabies/casedefinitions/ 

Single case

• People who work with animals (farmers, veterinarians, livestock breeders) or animal products such as wool, hides or hair (butchers, weavers).
• People who own dogs.
• People who work with the virus.
• People living in known rabies  endemic areas with low dog vaccination rates, and/or lack of infection prevention and control measures during and after a known outbreak are at higher risk. 

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities. 

•   Usually high without the administration of PEP. 

• Anyone bitten by an infected dog (or other animal) without pre-exposure prophylaxis or post-exposure vaccination. 

Rabies virus. It primarily affects the central nervous system. It travels through the nerves centripetally and centrifugally to the brain and other other organs respectively.  

Zoonotic disease: It occurs primarily in dogs with some wild animals such as raccoons, foxes, jackals, mongooses also serving as carriers. Humans get infected through the bites and scratches of an infected animal. There are no documented records of a human-to-human transmission.  

1. Bite and Scratch Wounds: 

The primary mode of transmission is through the bite or scratch of an infected animal. The virus is present in the saliva of rabid animals and enters the human body through broken skin or mucous membranes. 

2. Non-Bite Exposure: 

Although less common, rabies can be transmitted when the saliva or neural tissue of an infected animal comes into contact with mucous membranes (eyes, nose, mouth) or an open wound . 

Organ transplantation: Rabies has also been transmitted through organ transplants from infected donors, although this is extremely rare (CDC, 2022). 

The incubation period for rabies typically ranges from 1 to 3 months but can extend from a few days to several years and this is influenced by; 

• the location and severity of the bite
• the viral load
• the proximity to the central nervous system. 

Human-to-human transmission is possible but has not been confirmed. 

Furious (Encephalitic) Rabies:  The prodromal phase, which lasts 2-10 days, involves nonspecific symptoms like fever, headache, malaise, and pain or paresthesia at the site of exposure. As the virus ascends the nervous system, the patient enters the acute neurologic phase where aerophobia, hydrophobia, difficulty in swallowing, hyperexcitability, aggressive behaviour, confusion, and hallucinations are commonly seen. Autonomic nervous system dysfunction also leads to hypersalivation, sweating, and unstable blood pressure. As the disease progresses, coma sets in which eventually leads to death due to respiratory or cardiac arrest. 

Paralytic (Dumb) Rabies: Paralytic rabies often begins with muscle weakness and loss of sensation at the site of exposure. This progresses to full-blown paralysis, starting in the extremities and moving upwards. There is also a lack of hyperactivity or aggressive behaviour, making it harder to diagnose. As the disease progresses, paralysis spreads to the respiratory muscles, leading to respiratory failure which often leads to death, without any intervention. Paralytic rabies is nearly always fatal, with death occurring within days to weeks after the onset of symptoms if left untreated.  

West Nile fever, Eastern Equine Encephalitis, Japanese Encephalitis, Clostridium tetani infection, cerebral malaria, bacterial meningitis, leptospirosis, Marburg fever, Lassa fever.

Note: Clinical diagnosis of rabies remains challenging, as current diagnostic tools are generally unable to detect the virus before the onset of clinical symptoms. As a result, definitive diagnosis typically occurs in the late stages of the disease or post-mortem. 

Diagnostic confirmation includes: 

• Isolation of Lyssa virus from a clinical specimen
• Detection of Lyssa virus nucleic acid in a clinical specimen (e.g. saliva or brain tissue)
• Detection of viral antigens by a DFA in a clinical specimen
• Lyssa virus specific antibody response by virus neutralisation assay in serum or CSF 

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of a treatment or vaccine should be conducted by a health professional.  

• At the instance of a reported dog bite, wash the site of bite with detergents and water. Rabies virus is susceptible to detergents.
• Rabies can be prevented by vaccinations in dogs and humans.
• There is also a vaccine licensed to post exposure to the virus.

Rabies vaccination results in immunity for a minimum period of 1 year.