Rabies is a dangerous viral disease that is transmitted through the saliva of infected animals. If left untreated, rabies has a nearly 100% fatality rate. But how long after exposure can rabies develop before you start showing symptoms?
What is rabies?
Rabies is caused by a virus in the Rhabdoviridae family. It attacks the nervous system, causing inflammation of the brain and spinal cord. Rabies can affect any warm-blooded animal, but it is most commonly found in wild animals like foxes, raccoons, skunks, and bats.
The rabies virus is transmitteded through the saliva of an infected animal, usually through a bite wound. Less commonly, it can be transmitted if the saliva comes into contact with mucous membranes or an open wound. Once in the body, the virus travels through the nerves towards the brain.
Rabies causes neurological symptoms because of its ability to infect nerve cells. As the virus travels through the nervous system, it causes inflammation of the brain and spinal cord that leads to the signs and symptoms of rabies.
Rabies incubation period
The incubation period is the time from exposure to the rabies virus to when symptoms first appear. For rabies, this can range from a few days to several years. However, the incubation period is typically 1-3 months.
According to the CDC, the incubation period averages between 3-12 weeks. This means most people do not show rabies symptoms until at least 3 weeks after the initial exposure, although it depends on several factors.
Factors affecting the rabies incubation period
Several key factors determine the length of the rabies incubation period:
- Location of the bite wound or exposure – Bites on the head or neck can result in a shorter incubation period as the virus reaches the brain more quickly.
- Amount of virus transmitted – A severe bite or exposure to a large amount of infected saliva may contain more rabies virus and speed the onset of symptoms.
- Age and health status – Younger people and those with stronger immune systems may have longer incubation periods as their body fights the virus.
- Animal transmitting rabies – Some animals like bats and foxes seem to transmit a more virulent form of rabies than others.
Due to these factors, reported rabies incubation periods have ranged from less than 10 days to over 6 years in rare cases. But again, the typical incubation is between 3 weeks to 3 months after exposure.
Shortest known rabies incubation period
While rabies incubation usually lasts weeks to months, very short periods have been reported. The shortest known rabies incubation period is just 9 to 10 days.
This extremely short time from exposure to symptoms was documented in two rare cases of laboratory workers accidentally exposed to very high doses of the rabies virus. When high concentrations of the virus are introduced directly into nerves or the brain, symptoms can rapidly occur within about 10 days.
Longest known rabies incubation period
On the other end of the spectrum, the longest recorded incubation period for rabies is 6 years after exposure. However, very long incubation periods over 2-3 years are extremely rare.
A case study describes a 15-year old boy in Iran who died of rabies 6 years after being exposed when he was attacked by a stray dog. He did not receive postexposure treatment after the bite. Then 6 years later, he developed symptoms including anxiety, headaches, fever, vomiting, hydrophobia (fear of water), and aerophobia (fear of air). He tragically died 18 days after the onset of symptoms.
While this case documents the longest known rabies incubation at 6 years, nearly all cases will become symptomatic within 1-3 years at most.
When do rabies symptoms start?
The timeframe when rabies symptoms first appear depends on the length of the incubation period, which varies significantly between cases. But on average:
- 50% of people show initial symptoms at 30-90 days after exposure
- 80% of people develop symptoms within 90-150 days post-exposure
- Nearly 100% of cases will become symptomatic within 240 days (8 months) of the rabies exposure
So while a few rare cases have had incubation periods over 6 years, virtually all cases of rabies start causing symptoms within 8 months. Many cases become symptomatic much sooner, at around 2-3 months on average.
Early symptoms of rabies infection
The first rabies symptoms can be nonspecific and similar to having the flu. Early signs include:
- Fever
- Headache
- General weakness and discomfort
- Loss of appetite
- Nausea
- Vomiting
- Fatigue
As the infection progresses, more specific neurological symptoms arise due to the inflammation in the brain and spinal cord. These include:
- Tingling, prickling, or itching around the bite area
- Hallucinations
- Agitation and anxiety
- Confusion and delirium
- Insomnia
- Partial paralysis
A notable symptom that arises is hyperactivity and agitation when presented with stimuli like light, noise, or water. This progresses to the most characteristic sign of rabies which is hypersensitivity to swallowing liquids, known as hydrophobia (fear of water).
How does rabies progress?
As rabies enters its final stage, the virus causes severe neurological effects leading to death within a week or two. The symptoms progress as follows:
- Prodrome phase: First signs like fever, headache, weakness. Lasts 2-10 days.
- Acute neurological phase: Hyperactivity, hydropohobia, hypersalivation, hallucinations. Lasts 2-7 days.
- Coma and paralysis: Decreased consciousness progressing to coma. Death usually occurs within 48 hours of coma due to respiratory failure.
Without treatment, rabies has a nearly 100% fatality rate once symptoms are present. Even with advanced care, survival is extremely rare once the patient has developed severe neurological deficits.
How is rabies diagnosed?
Because rabies symptoms can be vague at first, it may not be diagnosed right away. However, doctors may suspect rabies in anyone with a fever and neurological symptoms who has been bitten by a wild animal or has another likely rabies exposure. Tests used to confirm the diagnosis can detect the rabies virus, antibodies, or viral genetic material in infected tissue, blood, or fluids.
Samples to test may include:
- Saliva
- Serum
- Spinal fluid
- Skin biopsy of hair follicles at the nape of the neck
Diagnostic tests for rabies include:
- Direct fluorescent antibody test: Detects rabies virus from a sample taken shortly after symptoms start.
- Rabies serology: Measures antibodies against the rabies virus that the body starts producing.
- RT-PCR: This molecular technique detects rabies genetic material in saliva, skin, or spinal fluid.
- Virus isolation: Growing the rabies virus from a sample to confirm the presence of the pathogen.
Is there treatment for rabies?
Unfortunately there is no effective treatment for rabies once symptoms appear. At this stage the disease is virtually always fatal, even with intensive hospital care and antiviral medications. That’s why postexposure prophylaxis is critical after any potential rabies exposure, before symptoms start.
Postexposure treatment with a series of rabies vaccinations is highly effective at preventing the disease if given shortly after exposure. However, treatment is focused on providing comfort care once rabies symptoms have developed.
Research is underway to find better treatments that could potentially save lives even after rabies symptoms start. Novel antiviral drugs as well as immunotherapy approaches are being investigated. But currently, no reliable cure exists once the disease has progressed.
Can you have rabies without symptoms?
No, rabies cannot cause an asymptomatic infection. People cannot become carriers of the virus without signs of infection. Once exposed, either rabies symptoms will present or the body clears the virus. The virus cannot persist in the body silently.
However, rabies can have a long incubation period where the person shows no symptoms for weeks to months. But they will eventually develop symptoms if untreated. The only exceptions could be extremely rare cases with years-long incubation periods.
How long can you have rabies before it kills you?
Without preventive treatment, rabies has an almost 100% fatality rate. After symptoms begin, survival is extremely rare. Most patients die within 7-10 days after symptoms start as the infection progresses to coma and respiratory failure.
The longest reported survival after onset of rabies symptoms is about one month. There are a handful of exceptional cases of patients living 6 weeks or slightly longer with intensive hospital care, although nearly all have still died. Overall, expect a survival time of only 1-2 weeks on average once rabies becomes symptomatic.
Can you recover from rabies?
Spontaneous recovery from rabies after onset of symptoms is essentially impossible. Once the virus causes severe neurological symptoms, death usually occurs within days to weeks even with aggressive treatment in the ICU.
Worldwide, less than 15 people are believed to have ever survived clinical rabies without preventive treatment prior to symptom onset. Many of these cases are disputed. So while survival may technically be possible, it is exceptionally rare.
This is why postexposure prophylaxis is so important after any bite, scratch or exposure where rabies transmission may have occurred. Preventive vaccination can prevent the virus from causing disease during the incubation period, before symptoms appear.
How common is rabies in humans?
Worldwide, rabies causes an estimated 59,000 human deaths per year, primarily in Africa and Asia. In the United States, human rabies deaths are extremely rare thanks to animal control programs and availability of postexposure treatment.
Only 1 to 3 rabies deaths are reported each year in the US. The majority of these result from bat strains of rabies virus. International travel and exposures abroad account for some of the rabies cases in Americans.
The number of rabies deaths has decreased dramatically in the last century thanks to vaccination of domestic animals and greater public awareness. However, rabies remains a persistent threat to both animal and human health that requires ongoing prevention and control measures.
Key points about the rabies incubation period
- Typical incubation period is 3-12 weeks, but can range from days to years.
- Most cases become symptomatic within 90-150 days after exposure.
- Shortest known incubation is just 9-10 days.
- Longest known incubation is 6 years, but very long periods over 2 years are rare.
- After symptoms start, survival is extremely uncommon.
- Postexposure vaccination can prevent disease during the incubation period before symptoms appear.
Conclusion
In conclusion, how long can you have rabies before knowing? The incubation period after rabies exposure is highly variable but typically lasts about 3-12 weeks. In rare cases it may be as short as 10 days or as long as 6 years. However, most people will develop initial flu-like symptoms within 30-150 days after being infected.
Rabies is almost always fatal once clinical signs appear, usually causing death within days to weeks. But postexposure vaccination started promptly after any exposure can prevent disease by stimulating immunity during the incubation period prior to symptom onset. Knowing the risk and seeking fast medical care after possible rabies contact is crucial to prevent this deadly outcome through preemptive treatment.