Information about the Rabies Virus for People Living in Hong Kong

Hong Kong is one of the few places in the world that is rabies-free. However, Hong Kong shares a land border with the Mainland where rabies is endemic and the mainland is the most likely source of rabies in Hong Kong. In 2020, 188 people died from rabies in China - 88 victims less than the previous year.²

No indigenous case of rabies has been reported in Hong Kong for years, and a rabies control programme is in place to guard against reintroduction of rabies into Hong Kong. However, international or national travellers may acquire the infection from rabies-endemic countries/areas and present with illness while in Hong Kong.³ 

Rabies is a vaccine-preventable, zoonotic, viral disease. Once clinical symptoms appear, rabies is untreatable.⁴  It is a rare but severe infection of the brain and nerves.⁵ It can spread to people and pets if they are bitten or scratched by a rabid animal.⁶ 

According to the World Health Organization, the fatality rate is almost 100% in humans and animals alike, affecting approximately 59,000 people every year. Of these cases, 99% are acquired from the bite of an infected dog.⁴ Every year, more than 29 million people worldwide receive a post-bite vaccination. This is estimated to prevent thousands of rabies deaths annually.⁴

What is Rabies?

The rabies virus (狂犬病病毒) infects the central nervous system, particularly causing inflammation in the brain (encephalitis). The incubation period is usually 1-3 months but can vary from less than one week to over one year.⁷ The key to fighting the virus is a quick response.

Transmission of Rabies in Humans

Bites and Scratches

Rabies virus is transmitted through direct contact with saliva or brain/nervous system tissue from an infected animal. People usually get rabies from the bite of a rabid animal. Domestic dogs, cats, rabbits, and wild animals such as skunks, raccoons, and bats can transfer the virus to humans via bites and scratches.⁸  It is possible to get rabies from non-bite exposures from a rabid animal, which can be scratches, abrasions or open wounds that are exposed to saliva or other potentially infectious material.⁹ 

Others

Other modes of transmission are uncommon. Inhalation of aerosolised rabies virus is one potential non-bite route of exposure, but mostly only laboratory workers encounter an aerosol of rabies virus. Rabies transmission through solid organ and corneal transplants are recorded. Most organ procurement organisations add a  screening question about rabies exposure for evaluating the suitability of each donor.⁹ 

Bites and non-bites exposures from a person infected with the rabies virus can theoretically transmit rabies, but no cases are documented. Therefore, contact with rabies-vaccinated individual does not pose a risk for infection, does not constitute rabies exposure, and does not require postexposure prophylaxis (PEP).⁹ 

Rabies virus becomes non-infectious when it dries out and when it is exposed to sunlight.⁹ 

Symptoms of Rabies

After a bite or other rabies exposure, the rabies virus travels through the body to the brain before it can cause symptoms.¹⁰ The initial  symptoms of rabies are similar to those of the flu, including:¹⁰

• General weakness
• Discomfort
• Fever
• Headache

These symptoms last for days. Without treatment, the symptoms of rabies will usually start after 3 to 12 weeks, although they can start sooner or much later than this.⁵ As the virus spreads to the central nervous system, fatal and progressive inflammation of the spinal cord and brain develops. Other symptoms that start a few days later include:⁵ 

• Confusion or aggressive behaviour;
• Seeing or hearing things (hallucinations);
• Producing lots of salivae or frothing at the mouth;
• Muscle spasms;
• Difficulty swallowing and breathing;
• Inability to move (paralysis).

There are two forms of the disease:⁴

Furious Rabies:

This form of the disease results in signs of hyperactivity, excitable behaviour, hydrophobia (fear of water) and sometimes aerophobia (fear of drafts or fresh air). Cardio-respiratory arrest is the main cause of death from this type of rabies. 

Paralytic Rabies:

This form of the disease accounts for about 20% of the total number of human cases. It  usually runs a longer and less dramatic course than the furious form. Muscles gradually become paralysed, starting at the site of the bite or scratch. A coma slowly develops, and eventually leads to death. 

Rabies Risk Factors

Factors that can increase your risk of rabies include:¹¹

• Travelling or living in areas where rabies is more common such as countries in Africa and Southeast Asia;
• Activities that are likely to put you in contact with wild animals that may have rabies 
• Working in a laboratory with the rabies virus;
• Wounds to the head or neck, that may allow the rabies virus to travel to your brain more quickly.

How is Rabies Diagnosed?

In animals, rabies is diagnosed using the direct fluorescent antibody (DFA) test, which looks for the presence of rabies virus antigens in brain tissue. 

In humans, several tests are required. Accurate and rapid laboratory diagnosis of rabies in humans and other animals is essential for the timely administration of postexposure prophylaxis.¹² However, when  a rabid animal bites you, there is no way to determine whether the animal has transmitted the rabies virus to you. Thus, treatment to prevent the rabies virus from infecting your body is recommended if the doctor thinks there is a chance that you have been exposed to the virus.¹³ 

Treatment for Rabies

Once the symptoms begin to appear, it usually means that the virus has reached the brain nerves. Therefore, if you think that you have been exposed to rabies, you must contact your doctor to get a series of shots to prevent the infection from spreading.

Medical Treatment for humans bitten by rabies-infected animal:

If you have been bitten by a rabid animal, you will receive a series of shots to prevent the rabies virus from infecting you. Rabies shots include:¹³ 

1. Fast-acting shot (rabies immune globulin), a type of injection is given near the area where the animal bit you as soon as possible after the bite;
2. A series of rabies vaccinations may be provided to help your body learn to identify and fight the rabies virus. Rabies vaccinations are given as injections in your arm. You receive four injections over the period of 14 days.

Self-Treatment for humans scratched by an animal:

If you have been scratched or bitten by an animal in a risky area:¹³ 

1. Immediately clean the wound with running water and soap for several minutes;
2. Sanitise  the wound with alcohol or iodine-based disinfectant and apply a simple dressing;
3. Go to the nearest medical centre, hospital, or a GP as soon as possible and explain that you have been bitten or scratched.

If possible, obtain the name and the address of the owner of the animal so that the animal can be observed for ten days to see whether it begins to behave abnormally.

Rabies Vaccine in Hong Kong

The rabies vaccine is an active immunising agent to prevent infection caused by the rabies virus. The vaccine works by causing your body to produce antibodies against the virus for protection. The rabies vaccine is used in two ways: pre-exposure prophylaxis and post-exposure prophylaxis.¹⁴ 

The rabies vaccine is not recommended for the public for pre-exposure rabies vaccination. It is given to people at increased  risk to protect them if they are exposed. People at high risk of exposure to rabies include:¹⁵ 

1. Veterinarians, animal handlers and veterinary students;
2. Rabies laboratory workers;
3. Spelunkers (people who explore caves);
4. People who work with the live vaccine to produce rabies vaccine and rabies immune globulin.

Pre-exposure rabies vaccination should also be considered for:¹⁵ 

• People whose activities bring them into frequent contact with the rabies virus or with possibly rabid animals;
• International travellers who are likely to encounter animals in parts of the world where rabies is common and immediate access to appropriate care is limited.

For pre-exposure vaccination, three doses of inactivated rabies vaccine on days 0, 7, 21 or 28 is given as the standard primary series. Active immunity develops after the third dose; thus, pre-exposure vaccination should be started one month before travelling. Travellers who wish to take the anti-malaria (chloroquine) should preferably be given a vaccine intramuscularly because concurrent use of these drugs may affect the antibody response to the intradermal vaccination.¹⁶ People who may be repeatedly exposed to the rabies virus should receive periodic testing for immunity, and booster doses might be necessary. 

For post-exposure vaccination, rabies vaccine can prevent rabies if given to a person after exposure. Anyone who has been bitten by an animal suspected to have rabies or who otherwise may have been exposed to rabies should clean the wound and see a health care provider immediately regardless of vaccination status. 

Side-Effects of Rabies Vaccines

After receiving the rabies vaccine, some people may develop temporary symptoms such as soreness, redness or itching and swell at the injection site for 24 to 48 hours.¹⁷

Other potential symptoms include:¹⁵ 

• Headache, nausea, abdominal pain, muscle aches, or dizziness;
• Hives, pain in the joints or fever after the booster doses;
• In rare cases, nervous system disorders have been reported.

Talk to your healthcare provider to discuss the vaccination and vaccine side-effects. 

Prevention of Rabies

Understanding your rabies risk and knowing what to do after contact with animals can help save lives. Any mammal can get rabies; thus the best way to avoid rabies is to stay away from wildlife or dogs. If you find an injured animal, do not touch it and contact local authorities for assistance.¹⁸ 

Because pets can get rabies from wildlife and then spread it to humans, preventing rabies in pets is also an important step in preventing human rabies cases.¹⁵  

To reduce your risk of encountering rabid animals:¹⁸ 

• Vaccinate your pets;
• Keep your pets confined;
• Protect small pets from predators;
• Report stray animals to local authorities;
• Do not approach wild animals;
• Keep bats out of your home;
• Consider the rabies vaccine, if you are travelling.

If you encounter a rabid animal, remember that rabies in humans is 100% preventable through prompt, appropriate medical care. If you are bitten, scratched or unsure, talk to a healthcare provider to see whether you need post-exposure vaccinations.¹⁸ Visit our blog to learn more about adult vaccinations in Hong Kong.

Help at OT&P Healthcare

OT&P Healthcare has a dedicated team of general practitioners who will be able to guide you to identify an appropriate solution to prevent rabies.

We also provide a range of vaccination services at all our clinics. Click here to learn about the immunisation program in Hong Kong.

You can also book an appointment or call our registration desk to learn more. For information on other vaccinations, you can check our vaccine calculator. 

References

1. (2021). Annual number of deaths from rabies in China from 2015 to 2020 - survey. Statista. March. Available at: <https://www.statista.com/statistics/861154/fatalities-from-rabies-in-china/>
2.  ‘Scientific Committee on Emerging and Zoonotic Diseases Prevention and Control of Rabies’. Centre for Health Protection. Available at: <https://www.chp.gov.hk/files/pdf/prevention_and_control_of_rabies_r.pdf>
3. (2021). ‘Rabies’. World Health Organization. 17 May. Available at: <https://www.who.int/news-room/fact-sheets/detail/rabies>
4. (2020). ‘Rabies’. NHS. 9 January. Available at: <https://www.nhs.uk/conditions/rabies/>
5. (2021). ‘Rabies’. Centers for Disease Control and Prevention. 23 September. Available at: <https://www.cdc.gov/rabies/index.html>
6. (2019). ‘Rabies’ Centre for Health Protection. 3 December. Available at: <https://www.chp.gov.hk/en/healthtopics/content/24/3149.html> 
7. Shannon Johnson, Meredith Goodwin, MD, FAAFP. (2021). ‘Rabies’. Healthline. 14 September. Available at: <https://www.healthline.com/health/rabies>
8. (2019). ‘How is rabies transmitted?’ Centers for Disease Control and Prevention. 11 June. Available at: <https://www.cdc.gov/rabies/transmission/index.html>
9. (2019). ‘What are the signs and symptoms of rabies?’ Centers for Disease Control and Prevention. 11 June. Available at: <https://www.cdc.gov/rabies/symptoms/index.html>
10. (2019). ‘Rabies: Symptoms & Causes’. Mayo Clinic. 6 Dec. Available at: <https://www.mayoclinic.org/diseases-conditions/rabies/symptoms-causes/syc-20351821>
11. (2011). ‘How is rabies diagnosed?’ Centers for Disease Control and Prevention. 22 April. Available at: <https://www.cdc.gov/rabies/diagnosis/index.html>
12. (2019). ‘Rabies: Diagnosis & Treatment’. Mayo Clinic. 6 Dec. Available at: <https://www.mayoclinic.org/diseases-conditions/rabies/diagnosis-treatment/drc-20351826>
13. (2021). Rabies Vaccine (Intramuscular Route). Mayo Clinic. 1 September. Available at: <https://www.mayoclinic.org/drugs-supplements/rabies-vaccine-intramuscular-route/description/drg-20069868>
14. (2020). Rabies VIS. Centers for Disease Control and Prevention. 8 January. Available at: <https://www.cdc.gov/vaccines/hcp/vis/vis-statements/rabies.html>
15. (2020). Vaccine and Prophylaxis. Travel Health Service. 28 December. Available at: <https://www.travelhealth.gov.hk/english/vaccine_prophylaxis/rabies.html>
16. (2020). Rabies - Vaccination. NHS. 9 January. Available at: <https://www.nhs.uk/conditions/rabies/vaccination/>
17. (2019). ‘How can you prevent rabies in people?’ Centers for Disease Control and Prevention. 11 June. Available at: <https://www.cdc.gov/rabies/prevention/people.html>