Recently, it was reported that a 48-year-old man from Shengzhou sought treatment at a hospital in Hangzhou and was diagnosed with rabies, tragically passing away just 3 days later!
The man visited the hospital on the evening of March 27th, describing having had a low-grade fever for several days. He feared drafts, as they made him feel tightness in his chest and discomfort in his throat. He constantly felt thirsty but was apprehensive about drinking water.
During the consultation, he exhibited restlessness and was unable to sit still.
Upon preliminary examination, doctors suspected rabies and inquired whether he had ever been bitten or scratched by a cat or dog in the past, to which the man denied.
To confirm their suspicion, doctors prescribed laboratory tests, revealing the presence of the rabies virus in his cerebrospinal fluid.
Three days later, when doctors attempted to follow up with a phone call, they sadly discovered that the man had passed away. His wife disclosed a crucial detail: "He was bitten by a dog several years ago!"
The news immediately went viral after it came out:
"A bite from years ago still causing symptoms? Can rabies really have such a long incubation period?"
"Why let the man go if it's confirmed to be rabies? Why didn't the doctors initiate treatment? Maybe there could still have been a chance to save him!"
"No wonder people always say rabies can incubate for up to 19 years. I guess I believe it now."
Before jumping to conclusions, let's first understand rabies.
Rabies, caused by the rabies virus, is a deadly neurological disease with an almost 100% fatality rate once symptoms develop.
It's a zoonotic disease, meaning it can be transmitted from animals to humans, primarily through bites or scratches from infected animals, with dogs being responsible for 99% of human cases.
The disease is most prevalent in Africa and Asia globally. In the Americas, where dog control is more effective, rabies mainly comes from bat bites, accounting for only 5% of cases from dogs.
Once rabies symptoms appear, the fatality rate is nearly 100%. This is because the virus infects the nervous system, with a long asymptomatic incubation period and no highly effective way to detect the virus, often leading to oversight until it's too late once the virus reaches the brain.
Rabies manifests in several stages:
Incubation Period: Following a bite from an infected animal, if vaccination isn't promptly administered, the virus enters the body with the animal's saliva. Even exposure of a wound to the licked area can lead to infection.
During this phase, there are no symptoms. However, the virus isn't idle. It enters through the wound, first replicating locally, then traveling along nerves throughout the body, with the ultimate target being the brain.
During the incubation period, the virus quietly resides without actively affecting the body because it hasn't yet occupied major sites such as the spinal cord and brain.
Symptoms Onset: Early symptoms include fatigue, headache, and fever. Although the wound may have healed, most individuals may experience itching at the site of the bite during this phase.
Gradually, symptoms resembling fear, excitement, insomnia, and anxiety emerge.
Furious Stage:
This stage presents typical rabies symptoms, such as hydrophobia (fear of water), aerophobia (fear of drafts or wind), difficulty swallowing, reluctance to drink water, and drinking without quenching thirst.
The onset of these symptoms indicates that the virus has invaded the brain. Once it takes over the salivary glands, it secretes large amounts of saliva to produce more viruses (which are present in the saliva). Under its control, patients refrain from drinking water and may exhibit aggressive behavior because drinking water would dilute the virus content, and aggressive behavior, such as biting, is the most effective way to spread the virus.
It can be said that the ultimate goal of the virus is reproduction and transmission.
Coma Phase:
After the frenzy, the body eventually enters a quiet state.
This is because in the late stage, vital organs are severely damaged, and most basic functions can no longer be maintained, resulting in limb paralysis, and the virus has also achieved its goal of reproduction and spread. A few days later, the patient will die.
In some cases, the virus may also have difficulty controlling its virulence, with intense initial infection leading some patients to skip the frenzy phase and directly enter the most severe paralysis phase.
The man mentioned at the beginning was already in the frenzy phase and died three days after seeking medical attention, which is consistent with the course of rabies.
Generally, the onset of rabies lasts for 7-10 days, ultimately leading to death due to respiratory failure, organ failure, and other reasons.
How long is the incubation period of rabies?
Generally, from infection to symptom onset, the incubation period of rabies is 1-3 months.
The length of the incubation period refers to the spread time of the virus, which is influenced by many factors, such as:
The location of the bite: The closer to the brain, the shorter the path and the shorter the incubation period.
The state of the animal at the time of biting (viral load): If the animal is in the frenzy phase, it means a high concentration of virus in the saliva, leading to more virus entering the wound, thus shortening the incubation period.
The type of rabies virus: There are many types of rabies virus, and different types have different incubation periods.
It is precisely because of the individual variability of rabies that there are some rare extreme cases.
According to past case statistics, incubation periods of less than one month (the shortest being 4 days) account for 30%; 1-3 months account for 54%; over 3 months account for 15%; and over 1 year account for 1%.
Case: "A Human Rabies Case with a Long Incubation Period in Wuhan City," published on November 4, 2020. A 63-year-old woman in Wuhan developed symptoms on May 6, 2018, three years after being bitten by a dog.
Case: "Phylogenetic and Epidemiologic Evidence of Human Rabies Infection with Long Incubation Period," published on January 23, 2014. A man diagnosed in the United States eight years after immigrating from Brazil. The virus isolated from him was of the Latin American dog rabies virus strain, which was not present in the United States. Therefore, his rabies incubation period was confirmed to be eight years. Before leaving Brazil, he had handled dog carcasses.
Case: "Rabies Encephalitis Incubation Period Could Be as Long as 25 Years!" published from July to September 2012. A 48-year-old male in India experienced rabies symptoms in November 2009. He recalled being bitten on the leg 25 years prior. Researchers investigated his work, home environment, and social interactions. Based on the investigation, it was highly likely (but not certain) that the incubation period was 25 years.
These cases demonstrate that cases of rabies with incubation periods of over a decade do occur. However, most scientists still consider the claim that "rabies incubation period can be over a decade" to be lacking scientific evidence. This is because such cases are rare, and many have long intervals between exposure and symptoms, leading to issues like incomplete investigations and patient misinterpretation.
It's worth noting that only when bitten by an animal carrying the rabies virus and the virus enters the body does a person become infected. Timely vaccination intervention after a bite can prevent the disease from developing 100%.
Those who harbor a sense of luck often miss the optimal treatment window. Once the disease manifests, treatments are usually ineffective.
Some have recovered, with global rabies cure data reaching 29 individuals by 2019. Perhaps these individuals possessed strong vitality or were exceptionally fortunate, surviving with the cost of enduring lifelong sequelae.
Unfortunately, their treatment experiences cannot be replicated. The same treatment regimen yields vastly different results for different individuals, rendering it non-generalizable.
In other words, with current scientific knowledge, the fatality rate of rabies remains at 100%.
However, I believe that conquering rabies isn't far off. Chinese scientists discovered a genetic switch that inhibits the rabies virus a few years ago.
