Rabies incubation period
Hello, doctor.
About six years ago, I was scratched by a wild cat.
At that time, I wasn't sure if I received the rabies vaccine (because I heard that the rabies vaccine requires multiple doses; I remember getting two shots, one for tetanus and I forgot the other).
I didn't pay much attention to it afterward, but later I heard that rabies can have an incubation period of up to seven years.
Is it still possible for me to develop the disease after such a long time?
Jiang Xiansheng, 20~29 year old female. Ask Date: 2021/09/03
Dr. Xiao Yongxun reply Family Medicine
Dear Mr.
Jiang:
1.
The rabies virus is a rod-shaped virus belonging to the Lyssavirus genus.
All viruses in this genus share similar antigens, but monoclonal antibodies or nucleic acid sequencing can differentiate viruses from different regions or animal sources.
Animals infected with rabies carry the virus in their saliva, which can enter the human body through wounds caused by scratches or bites from infected animals (in rare cases, through freshly injured skin or mucous membranes).
It is also dangerous to be scratched by the paws of animals infected with rabies, as they tend to lick their feet.
2.
The incubation period for rabies typically ranges from 1 to 3 months, but it can be as short as less than a week or as long as over a year; this depends on factors such as the severity of the wound, the density of nerve distribution in the wound area, the distance to the brain, the strain of the virus, the viral load, the degree of clothing protection, and other factors.
Early symptoms of rabies are nonspecific and may include fever, sore throat, chills, malaise, anorexia, vomiting, respiratory difficulties, cough, weakness, anxiety, and headache, or specific symptoms related to the site of the bite or scratch.
After several days, symptoms of agitation and fear may appear, followed by progression to paralysis, difficulty swallowing, and spasms of the throat muscles, leading to hydrophobia (also known as fear of water).
Subsequently, symptoms may include confusion and convulsions.
Without any medical intervention, patients typically die from respiratory paralysis within 2 to 6 days (sometimes longer).
3.
Regarding your statement that "rabies can have an incubation period of 7 years," I have not encountered any medical journal reports in clinical practice supporting this; I am curious about the source of this information.
In the case of scratches or bites from wild cats, our current recommendation is to observe or capture the cat for 10 days.
If the cat dies or shows symptoms, the patient who was bitten or scratched should consider receiving the rabies vaccine.
In fact, this has been the policy of the World Health Organization for decades and has not been overturned or questioned.
After all, the rabies virus enters through the wound and typically reaches the central nervous system and causes disease within a few weeks or months; a 7-year incubation period seems implausible.
4.
If you have further questions, I recommend discussing them with your family physician before making any decisions.
Reply Date: 2021/09/03
More Info
Rabies is a viral disease that primarily affects mammals, and it is most commonly transmitted through the saliva of an infected animal via bites or scratches. The rabies virus has a well-documented incubation period, which can vary significantly from a few weeks to several months, and in rare cases, it can extend to years. However, the notion that rabies can remain latent for as long as seven years is a misconception. The majority of rabies cases manifest symptoms within one to three months after exposure, and the likelihood of developing rabies decreases significantly after this period.
In your case, since the incident occurred approximately six years ago, it is highly unlikely that you would develop rabies now. The rabies virus typically does not have a latency period that extends beyond a year. If you had been infected, symptoms would have likely appeared much sooner. The symptoms of rabies can include fever, headache, confusion, agitation, hydrophobia (fear of water), and paralysis, among others. If you have not experienced any of these symptoms in the years following the incident, it is reasonable to conclude that you did not contract rabies.
Regarding your vaccination history, if you received two doses of the rabies vaccine, it is important to note that the rabies vaccination protocol typically requires a series of shots (usually four or five doses) administered over a specific timeframe after exposure to a potentially rabid animal. If you were unsure whether you completed the vaccination series, it would be prudent to consult with a healthcare provider for further evaluation. They may recommend a rabies titer test to check for immunity, although this is not commonly done unless there is a specific concern about exposure.
In addition to rabies, it is essential to consider other potential infections from animal scratches, such as bacterial infections. Cat scratches can lead to conditions like cat scratch fever, caused by Bartonella henselae, which can result in swollen lymph nodes, fever, and fatigue. If you have any lingering concerns about your health or if you experience any unusual symptoms, it is advisable to seek medical attention.
In summary, based on current medical understanding, the risk of developing rabies from a cat scratch that occurred six years ago is extremely low, especially if you have not exhibited any symptoms. However, if you have any ongoing health concerns or if you are feeling anxious about your past exposure, it is always best to consult with a healthcare professional who can provide personalized advice and reassurance.
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