傳染病於香港的現況 The Current Situation of Infectious Diseases in Hong Kong

1. 傳染病於香港的現況The Current Situation of Infectious Diseases in Hong Kong 香港瑪嘉烈醫院 內科及老人科部 傳染病科主任 黎錫滔醫生 Dr. Sik-To Lai, Consultant Physician and Head of Infectious Disease Department of Medicine and Geriatrics Princess Margaret Hospital Hong Kong SAR

2. “Today, infectious diseases are not only a health issue; they have become a social problem with tremendous consequences for the well-being of the individual and the world we live in.” Hiroshi Nakajima, MD, PhD Former Director-General World Health Organisation, 1996

3. Introduction • “The end of infectious diseases” was a popular idea in the 1970s • Infectious diseases are still important in the 21st century due to: • Boundless nature • Emergence of new infections • Re-emergence of old infections • Increase in drug - resistant infections

4. Incidence • 27 statutory notifiable infectious diseases in Hong Kong which are reported to the Department of Health (DH) of the Hong Kong SAR Government • The top five diseases in 2001 were chickenpox, tuberculosis, viral hepatitis, food poisoning and bacillary dysentery • No exact figure for non-notifiable infectious diseases in the community and hospitals. Many of these diseases are very important and numerous in number, e.g. influenza, otitis media, pneumonia, urinary tract infection etc.

5. Comparison of the Number of ID Notifications in 2000 with the Mean of 1995-1999

6. No. of Notifications for Notifiable Infectious Diseases in 2001 Cholera 38 Meningococcal infections 10 Plague 0 Mumps 76 Yellow fever 0 Paratyphoid fever 21 Acute poliomyelitis 0 Rabies (Human) 1 Amoebic dysentery 7 Relapsing fever 0 Bacillary dysentery 389 Rubella 57 Chickenpox 16,501 Scarlet fever 147 Dengue fever 17 Tetanus 4 Diphtheria 0 Tuberculosis 7,262 Food poisoning (outbreaks) 672 Typhoid fever 67 Food poisoning (affected) 2,709 Typhus fever 7 Legionnaires’ Disease 3 Viral hepatitis A 482 Leprosy 10 Viral hepatitis B 125 Malaria 47 Non-A, non-B hepatitis 39 Measles 182 Unclassified hepatitis 33 Total 26,212

7. Deaths from Notifiable Infectious Diseases • There were 310 deaths from notifiable infectious diseases in 2000 • 299 were due to tuberculosis (96%) • The rest were due to • Viral hepatitis 4 • Tetanus 2 • Chickenpox 1 • Malaria 1 • Meningococcal infections 1 • Rabies 1 • Typhoid fever 1

8. Surveillance and Management • Infectious disease surveillance is undertaken by the Disease Prevention and Control Division of the Department of Health • A number of DH and private clinics act as sentinel surveillance points • Notifiable infectious diseases are admitted into the Infectious Disease Unit of Princess Margaret Hospital. Three diseases are quarantinable, including cholera, plague and yellow fever • Non-notifiable infectious diseases are managed in clinics and hospitals at large

9. Important Infectious Diseases in Hong Kong • By the number and seriousness, there are 3 important infectious diseases in Hong Kong — tuberculosis, HIV/AIDS and sexually transmitted infections • These diseases are managed by special clinics and staff due to public health , expertise and resources considerations

10. Viral Hepatitis in Hong Kong 1988 - 2000

11. Hepatitis (1) • The incidence was 679 cases in 2001 • Hepatitis A — 482 • Hepatitis B — 125 • Non-A, non-B hepatitis — 39 • Unclassified hepatitis — 33 Hepatitis A • No major outbreak after 1992, apart from some minor outbreaks especially in mental institutions • Prevalence of hepatitis A antibody found to be 10% and 30% in people aged < 11 and < 30, respectively. Large pool of non-immune individuals • No formal hepatitis A vaccination programme from the government

12. Hepatitis (2) Hepatitis B • Hepatitis B vaccine is given to all newborns in Hong Kong • Overall carrier rate around 10% with much lower prevalence in children • Acute hepatitis B has become a largely sexually-transmitted disease • Interferon and antivirals are used in the treatment of chronic hepatitis B Hepatitis C • Found in 0.5% of blood donors • HCV Look Back Programme of the Hospital Authority • Interferon and ribavirin are used in the treatment of chronic hepatitis C Hepatitis E • 40% of non-ABC hepatitis • Similar picture to hepatitis A • 11% of hepatitis A have hepatitis E co-infection

13. Cholera • Mainly imported cases from neighbouring endemic areas • Contaminated shell-fish has been the culprit in many cases • Polluted seawater in fish tanks was implicated in some restaurant outbreaks • Minimal mortality but reports of acute renal failure in the elderly and ill • Fluoroquinolones are now drugs of choice • Vaccination is not recommended

14. Enteric Fever • Many cases are imported (13.4%) and most common in young adults • Cause of pyrexia of unknown origin • Previous antibiotic therapy renders blood culture negative • Maybe mistaken as surgical emergencies • Most common complication is gastrointestinal bleeding • Widal test is not clinically useful • Multi-drug resistant (MDR) strains are common • Fluoroquinolones are the drugs of choice • Chronic carrier rate of 2 – 5% • Oral and parenteral vaccines are available

15. Dysentery • The most common organism in bacillary dysentery is Shigella sonnei • Outbreaks have been reported in mental institutions • Similar clinical features are found in infection caused by Vibrio parahaemolyticus and Plesiomonas shigelloides • Fluoroquinolones are the drugs of choice

16. Food Poisoning • Compared with 1999, there was a 15% increase in the number of outbreaks and a 13% increase in the number of persons affected in 2000 • Majority of outbreaks were small (96%) affecting less than 10 persons • About half occurred in food premises and most of the rest occurred at home • Top five causative agents in terms of the number of outbreaks were: • Vibrio parahaemolyticus (36%) • Staphylococcus aureus (18%) • Salmonella spp. (14%) • Clenbuterol (6%) • Ciguatoxin (5%)

17. Viral Gastroenteritis • Commonly due to Norwalk-like viruses • Increase in number of outbreaks in Hong Kong • Residential homes and schools • Isolated cases among people of all age groups • Food may be contaminated at the source, e.g. oysters harvested from sewage contaminated water, or by food handlers • Aerosol spread also occurs from the vomitus • Prevention is by strict observance of food, environmental and personal hygiene

19. Malaria (1) • Around 80% are due to Plasmodium vivax and 17% are due to Plasmodium falciparum • The main areas of acquisition are China, Indian Subcontinent, Southeast Asia and Africa • Indigenous cases also occur • Low mortality of 5 out of 862 from 1991 – 2000. All the deaths were due to cerebral malaria and multi-organ failure in Plasmodium falciparum infection

20. Malaria (2) • Chloroquine is used for Plasmodium vivax, ovale and malariae • Quinine plus tetracycline or mefloquine alone are used for Plasmodium falciparum infection • Quinine-resistant cases of falciparum malaria were found and the patients had exposure in the Thai-Cambodia border • Artemisinin plus tetracycline / mefloquine have been used with success • Mefloquine is the preferred drug for chemoprophylaxis • Travel clinics run by the DH and PMH can offer advice, drugs and vaccines

21. Dengue Fever • Occasional cases in Hong Kong, all with a history of travel to endemic areas • The vector mosquito Aedes albopictus is found in Hong Kong • Outbreak of around 1500 cases in Macau last summer to autumn • No evidence of spread to Hong Kong • Diagnosis is by rise in antibody titre • No report of dengue haemorrhagic fever • Conservative treatment ± blood transfusion

22. Chickenpox / Herpes Zoster (1) • Became a notifiable infectious disease since Feb, 1999 • Top in incidence in 2001 — 16,501 cases • Most cases were children aged 10 or below • Southeast Asian domestic helpers (e.g. from the Philippines etc.) were most common among adult patients • Complications have been uncommon (< 1%) and in 2000 included • Scarlet fever (24) • Pneumonia (9) • Sepsis (4) • Other group A streptococcal infections (4) • There was one death involving an immunocompromised person in 2000

23. Chickenpox / Herpes Zoster (2) • Strict isolation in hospital • Early antiviral treatment shortens duration of symptoms and pain • Given within 24 hours of rash in chickenpox • Given within 72 hours of rash in herpes zoster • Antiviral therapy used for all cases of severe chickenpox or herpes zoster in the elderly or immunocompromised patients • Varicella-zoster immunoglobulin given within 96 hours of exposure can prevent / modify disease in contacts • Chickenpox vaccine is available and can achieve > 90% seroconversion

24. Measles • Immunisation programme for measles has been in place since 1967 • MMR (Measles, Mumps, Rubella) vaccine is given to children at 12 months of age and at primary one in Hong Kong • Adult cases of measles are still present due to failure to take the booster dose of vaccine and waning antibody titre • May cause severe disease in adults, especially pregnant women and immunocompromised patients • Respiratory isolation required • Immunoglobulin may be used within six days of exposure for susceptible contacts

25. Rubella • Disease is preventable by MMR vaccine • Problem of waning antibody titre as in measles • Booster dose at primary six is important especially for girls — prevention of congenital rubella of fetus in pregnancy (2 cases in 2000) • High notification rate of rubella in recent years especially in young adults • There were 4 cases of rubella encephalitis in the outbreak between 1996 – 1997 and 1 died

26. Mumps • Cases are continuously reported but there have been no epidemic outbreaks • Besides parotitis, the virus can cause orchitis, oophoritis, lymphocytic meningitis, pancreatitis, post-infectious encephalitis, thyroiditis and arthritis • Symptomatic treatment • NSAIDs but not corticosteroids for pain of orchitis

28. Influenza (1) • Not notifiable in Hong Kong • Trend is monitored by sentinel surveillance in DH and private clinics with regard to the number of influenza-like illness and sample isolates from nasopharyngeal aspirates and throat swabs • Peak season is spring in Hong Kong • The main circulating serotypes are: • H3N2 —A / Sydney / 5 / 97, Moscow / 10 / 99, Panama / 2007 / 99 - like virus • H1N1 —A / New Caledonia / 20 / 99 – like virus • B / Hong Kong / 330 / 01 – like virus has become the predominant B serotype since October 2001 and has replaced the B / Sichuan / 379 / 99 - like virus prevalent in the last few years • WHO recommends that the new vaccine for the Northern Hemisphere this year should consist of the Moscow, New Caledonia and Hong Kong strains

29. Influenza (2) • Can given rise to complications like secondary bacterial pneumonia, myocarditis, encephalitis, Guillain-Barré syndrome, etc. • Increases morbidity and mortality in the elderly and immunocompromised patients • Amantadine and rimantadine have been in use and are active against influenza A • Neuraminidase inhibitors like zanamivir and oseltamivir are active against influenza A and B • Influenza vaccines are available for influenza A and B and are usually given in November to December • Annual vaccination programme for residents of aged homes and patients of long - stay facilities

30. Meningococcal Infections • Notifications rose sharply from 3 cases in 1999 to 14 cases in 2000 and 10 cases in 2001 • All were sporadic cases affecting patients of different age groups • 3 cases were imported from Mainland China • Half of the cases presented with signs and symptoms of meningitis and the other half those of septicaemia • The predominant serogroup was B (5) and the other serogroups were W135 (3), A (1) and non-B (1) • No cases of death notified in recent 2 years

31. Rabies • Hong Kong had been free from rabies since 1988 until one case appeared in 1999 • After that case, another one appeared in 2001 • Both were Filipino domestic helpers who had a history of travel back to the Philippines • The first had a history of dog bite and the second did not • Diagnosed as viral encephalitis initially • Correct diagnosis was reached in the first one antemortem and in the second one postmortem

32. Legionnaires’ Disease • Presents as severe community-acquired pneumonia, mild cases will be missed • No reported case was proved by culture • Diagnosis was established by retrospective finding of rise in antibody titres in suspected cases • No nosocomial case in Hong Kong despite ubiquitous presence of the organism • Recent report of 3 cases in Hong Kong, 2 in October and 1 in December 2001 • All 3 patients were residents of the Kwun Tong area • ? Related to polluted water cooling tower

33. Leptospirosis • Notifiable occupational disease in Hong Kong • One case notified in June 2001 • The local geographical, economic and behavioural factors do not favour a high risk of exposure • Rodent infestation, flooding, skin abrasions and use of bare hands to touch possibly contaminated articles and probing drains are potential risk factors

34. Antibiotic Resistance • Growing global trend of microbial resistance to many antibiotics due to indiscriminate and extensive use • A sentinel surveillance system for antibiotic resistance was initiated by DH in 1999, comprising private clinics and GOPCs • DH published the “Guideline on Antimicrobial Use in Primary Health Care Clinics” in January 2002 • Physicians and microbiologists of the HA formed the Interhospital Multi-disciplinary Programme on Antimicrobial ChemoTherapy (IMPACT) in 1999 and published the second draft edition of the handbook “Reducing bacterial resistance with IMPACT” in July 2001

35. Methicillin-Resistant Staphylococcus aureus • Prevalence of nearly 60% of isolates in some hospitals in Hong Kong • Typically found in debilitated patients on antibiotics • Community-acquired infections are increasingly reported • Prevalence related to the use of antibiotics and degree of contact precautions, especially hand washing

36. Penicillin-Resistant Streptococcus pneumoniae • Prevalence of intermediate penicillin resistance in Streptococcus pneumoniae is more than 60% in Hong Kong • Resistance to other antibiotics like erythromycin, tetracyclines, co-trimoxazole and clindamycin • More liberal use of pneumococcal vaccine in broader categories of patients now seems justified

37. Bioterrorism • Worldwide threat of terrorism caused by agents of biological disasters after the 911 incident in USA • Joint Working Group between the Security Bureau, Department of Health and Hospital Authority formed in November 2001 • Guidelines for the management of suspected and confirmed cases of exposure to anthrax were formulated and promulgated • The Hospital Authority Task Force on Infection Control had also prepared fact sheets on smallpox, plague, botulism and viral haemorrhagic fevers for reference and use by HA hospitals

38. Recent Trend in Infectious Diseases in Hong Kong • Notifiable infectious diseases are limited in number • Infectious disease physicians are now concentrating their efforts on : • HIV/AIDS • Infections of immunocompromised patients • Neutropenic infections • Critical care infections • Nosocomial infections • Infection control • Antibiotic policy etc.

39. Conclusions • The prevention and treatment of notifiable infectious diseases in Hong Kong have reached international standard • The trend now for modern infectious disease physicians is to concentrate more on other activities like HIV/AIDS, infections in immunocompromised patients, nosocomial infections and antimicrobial resistance etc. • Public health education and disease awareness of Hong Kong citizens still needs to be intensified