Half year into the pandemic: Hong Kong chapter
description
Transcript of Half year into the pandemic: Hong Kong chapter
Half year into the pandemic: Hong Kong chapter
Dr. Thomas TsangController, Centre for Health Protection
October 17, 2009
Where are we now?
Laboratory confirmed cases(as of October 10, 2009)
• Cumulative: 30,225 • Dependent on testing policy
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
. . . . . . . . . . . . . . . . . . . . . . . . . . .
5 6 7 8 9 10
2009
Severe cases (嚴重個案)
Non-severe cases (非嚴重個案)
Num
ber
of c
ases
(個案數目
)
Weekly number of ILI patients attending DFCs
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 7 8 9 10 11 12
2009
No.
of I
LI c
ase
s a
tten
ded
DF
Cs
指定流感診所的流感樣求診個案數目
ILI consultation rate among sentinel GPs
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 2 3 4 5 6 7 8 9 10 11 12
Month (月)
Ra
te (
pe
r 1
00
0 c
on
sulta
tion
s)比
率 (
每1
00
0 個
診 症
)
2007 2008 2009
Institutional ILI outbreaks
0
50
100
150
200
250
300
350
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 2 3 4 5 6 7 8 9 1011 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10
2007 2008 2009
Nu
mbe
r of
out
bre
aks
(爆發數目
)
Influenza-like illness outbreaks (流感樣爆發個案)
% +ve for HSI among tested DFC patients
0
10
20
30
40
50
60
70
80
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 7 8 9 10 11 12
2009
Per
cent
age
test
ed p
ositi
ve fo
r H
SI a
mon
g D
FC
atte
ndee
s
指定流感診所求診者對人類豬型流感測試呈陽性反應的百分比
HSI: dominant strain of influenza virus
Percentage of flu virus among all flu viruses detected
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
. . . . . . . . . . . . . . . . . . . . . . . . . .
5 6 7 8 9 10
Pe
rce
nta
ge
of
flu v
iruse
s a
mo
ng
all
flu v
iruse
s d
ete
cte
d
HSI H3N2 H1N1 A (Not typed) B C
Age distribution & attack rate (May 1 – Oct 10)
67% : < 20 years old82% : < 30 years old
0500
1000150020002500300035004000450050005500600065007000
0-4
5-9
10-1
4
15-1
9
20-2
4
25-2
9
30-3
4
35-3
9
40-4
4
45-4
9
50-5
4
55-5
9
60-6
4
65-6
9
70-7
4
75-7
9
80-8
4
85 o
r abo
ve
Age group 年齡組別
Num
ber o
f cas
es 個案數目
02004006008001000120014001600180020002200240026002800
Atta
ck ra
te (c
ases
/ 10
0,00
0 po
pula
tion)
發病率
()
個案每十萬人口
HSI cases
Attack rate
Hospitalization and age (Jun 27 – Sep 27)
0
1000
2000
3000
4000
5000
6000
7000
8000
<=5 6 -- 11 12 -- 18 19-29 30-39 40-49 50-59 60-64 >=65
Age group 年齡組別
Num
ber o
f cas
es 個案數目
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
Perc
enta
ge re
quiri
ng h
ospi
talis
atio
n住院百分比
Admitted Not admitted Percentage requiring hospitalisation
Overall percentage of cases requiring hospitalization: 13.9%
Severe & fatal HSI (as of October, 14)
• 142 severe HSI infections– 0.46% of total laboratory confirmed cases– 83 males; 59 females– Aged 13 months - 93 years (median: 51 years)– 75% had underlying diseases/risk factors– 66% required intensive care– Nucleotide sequencing closely similar to circulating HSI strain
• 32 fatal cases– 23 males; 9 females– Aged 11 years - 93 years (median: 55.5 years)– Case fatality ratio = 0.1%– 88% had underlying diseases/risk factors
ILI outbreaks (Sep 1 – Oct 9)
• 1,076 ILI outbreaks
• 1,017 (94.5%) in schools– 150 (13.9%) in kindergartens / child care centres– 441 (41.0%) in primary schools– 404 (37.5%) in secondary schools– 22 (2.0%) in special schools
• 51 advised to suspend classes
Antiviral resistance
• 3 sporadic cases in HK– One case associated with post-exposure prophylaxis– No onward transmission of drug-resistant viruses
• Global situation (as of Sep 27)– 28 oseltamivir-resistant HSI isolates– All show same H275Y mutation that confers
resistance to oseltamivir, but not to zanamivir– Worldwide, > 10,000 specimens of HSI virus have
been tested and found to be sensitive to oseltamivir
Containment phase measures
• Case isolation
• Contact management– Quarantine– Direct Observed Chemoprophylaxis– Medical surveillance
• Border health measures
• Surveillance, hygiene campaigns, etc.
Mitigation phase measures• Schools
– Early summer break for primary schools, kindergartens, etc.– Suspension of schools with large HSI outbreak
• Designated Fever Clinics
• Management of serious cases
• Antiviral stockpile deployment
• Vaccination
• Surveillance, self-care, hygiene campaigns, etc.
Case fatality (as of October 4, 2009)
WHO Region
Cumulative total
Cases* Deaths
Africa 12,382 70
Americas 146,016 3,292
Eastern Mediterranean 12861 80
Europe > 59,000 > 193
South-East Asia 38,038 480
Western Pacific 109,926 410
Total > 378,223 > 4,525
1,462 deaths in 177,457 cases reported to WHO (August 13), crude case fatality rate = 0.82% (HK = 0.1%: intensive testing?)
Effect of community hygienic measures on respiratory viruses isolation (2003)
• Respiratory infections during SARS outbreak, Hong Kong, 2003 (Emerg Infect Dis. 2005 Nov;11(11):1738-41)– Effect of during SARS outbreak studied by comparing proportion of
+ve specimens of various respiratory viruses in 2003 with those from 1998 to 2002
– Community hygienic measures significantly reduced incidence of respiratory viral infections
Effect of school closure (2008 Easter, HK)
GOPCs (2008)*
0
3
6
9
12
15
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12
March April
Date
ILI c
ases
/ 1,
000
cons
ulta
tions
Sentinel GPs (2008)
0
10
20
30
40
50
60
70
80
90
100
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12
March April
Date
ILI
cases /
1,0
00 c
onsultations
2008
0
10
20
30
40
50
60
70
80
2 3 4 5 6 7 8 9 10 1112 1314 15 1617 1819 20 2122 2324 25 2627 2829 30 31 1 2 3 4 5 6 7 8 9 1011 12
March April
Date
Num
ber
of is
olat
es0
5
10
15
20
25
30
35
Per
cent
age
posi
tive
influenza isolates
Percentage
: school closure period
Influenza virus isolation at Public HealthLaboratory Centre
Sentinel ILI consultation rates (GOPCs/GPs)
What else from here?
‘In the 1918–1919 pandemic, 1st wave began in March 1918 and spread unevenly through United States, Europe, and possibly Asia over the next 6 months. Illness rates were high, but death rates in most locales were not appreciably above normal. A 2nd or fall wave spread globally from September to November 1918 and was highly fatal.’
Taubenberger JK, Morens DM. Emerg Infect Dis [serial on the Internet]. 2006 Jan [date cited]. Available from http://www.cdc.gov/ncidod/EID/vol12no01/05-0979.htm
“Asian Flu 1957”• May 1957: WHO received news of extensive influenza epidemics in
HK & Singapore
• Epidemics had begun at end of February in China
• In 6 months, every part of the world had experienced cases
• 1st wave: concentrated in school-aged children
• 2nd wave: followed disappearance of the first from 1 to 3 months later, causing very high rate of illness and increased fatalities and affected mostly elderly
• Estimated deaths > 2 millions
Avian influenza: assessing the pandemic threat. WHO. January 2005.
Mortality Distributions & Timing of Waves of Previous Pandemics
Miller MA, et al. N Engl J Med. 2009 May 7.
• More rapid population movement
• Higher prevalence of pre-existing medical conditions
• Medical advances, antibiotics, antivirals
What’s different in 21st century
Strategies• Surveillance
• Medical services
• Non-pharmacological measures– Hygiene, outbreak management,
social distancing, etc.
• Pharmacological measures– Antivirals– Vaccines
Seasonal flu & pneumococcal vaccination programs
• Government Vaccination Program
• Private doctors
– Childhood Influenza Vaccination Subsidy Scheme
– Elderly Vaccination Subsidy Scheme
Vaccination subsidy schemes• Government will subsidise:
– Elderly Vaccination Subsidy Scheme - eligible elders to receive influenza vaccine & pneumococcal vaccine from private doctors
– Childhood Influenza Vaccination Subsidy Scheme - children age between 6 months and less than 6 years to receive influenza vaccine from private doctors
Target groups for HSI vaccination
• Recommendations of Scientific Committees of CHP
– Healthcare workers
– Persons at higher risk of death and complications from HSI due to underlying medical conditions (including pregnancy)
– Children aged > 6 months and below 6 years old
– Elderly persons aged > 65
Patients with chronic diseases have much higher percentage of serious illnesses across all age groups
CategoriesNumber of severe cases#
Percentage of cases classified as ‘severe’ (%)
Number of fatal cases
Percentage of cases died (%)
<=5 years with chronic diseases 1 7.14% 0 0%
<=5 years without chronic diseases 2 0.12% 0 0%
6-11 years (primary school students) with chronic diseases 1 1.72% 0 0%
6-11 years (primary school students) without chronic diseases 1 0.05% 0 0%
12-18 years (secondary school students) with chronic diseases 1 1.45% 0 0%
12-18 years (secondary school students) without chronic diseases 2 0.07% 0 0%
19-64 years (adults) with chronic diseases 13 3.64% 3 0.84%
19-64 years (adults) without chronic diseases 31 0.53% 7 0.12%
>=65 years (elderly) with chronic diseases 13 15.48% 2 2.38%
>=65 years (elderly) without chronic diseases 1 1.85% 0 0%
#Information on chronic disease status is available in 12,795 cases out of the 14,363 cases
Elderly, young children, patients with chronic diseases have higher hospitalization rates
CategoriesTotal number of cases#
Percentage requiring hospitalization* (%)
<=5 years with chronic diseases 14 42.9%
<=5 years without chronic diseases 1,669 31.8%
6-11 years (primary school students) with chronic diseases 58 13.8%
6-11 years (primary school students) without chronic diseases 1,859 15.4%
12-18 years (secondary school students) with chronic diseases 69 24.6%
12-18 years (secondary school students) without chronic diseases 2,802 8.2%
19-64 years (adults) with chronic diseases 357 22.4%
19-64 years (adults) without chronic diseases 5,829 8.1%
>=65 years (elderly) with chronic diseases 84 60.7%
>=65 years (elderly) without chronic diseases 54 60.8%
#Information on chronic disease status is available in 12,795 cases out of the 14,363 cases*Calculation based on cases confirmed between 27 June and 7 September (in mitigation phase when only relatively serious cases require hospitalization)
Most severe cases occur in adults Elders and young children have highest rates of severe illness
Age groups
Number of cases classified as ‘severe’
Percentage of cases classified as ‘severe’ (%)
Reported severe cases / 100,000 population)
Number of fatal cases
Case fatality rate (%)
Deaths / 100,000 population
< 6 years 3 0.15% 1.10 0 0% 0
6-11 years (primary school students)
2 0.08% 0.58 0 0% 0
12-18 years (secondary school students)
3 0.09% 0.51 0 0% 0
19-64 years (adults) 44 0.66% 0.90 9 0.14% 0.18
65 years (elderly) 14 9.46% 1.55 3 2.03% 0.33
Young children have highest attack rates Young children and elders have highest hospitalization rates
Age groupsNumber of cases
Percentage of total cases (%)
Reported cases/100,000 population
Percentage of cases requiring hospitalization* (%)
< 6 years 1,961 13.7% 719.6 29.1%
6-11 years (primary school students)
2,359 16.4% 681.0 13.9%
12-18 years (secondary school students)
3,254 22.7% 554.6 8.0%
19-64 years (adults) 6,641 46.2% 135.5 9.0%
65 years (elderly) 148 1.0% 16.4 61.4%
Pregnant women have high percentage of hospitalization
CategoriesTotal number of cases
Percentage of all cases (%)
Percentage requiring hospitalization* (%)
Persons with chronic disease# 582 4.05% 27.8%
Pregnant women 97 0.68% 71.1%
HA staff 408 2.84% 3.0%
Age < 6 year without chronic illness 1,669 11.62% 31.8%
Age 65 years old without chronic illness 54 0.38% 60.8%
#Information on chronic disease status is available in 12,795 cases out of the 14,363 cases*Calculation based on cases confirmed between 27 June and 7 September (in mitigation phase when only relatively serious cases require hospitalization)
Background Incidence of GBS
Overseas Hong Kong
Background incidence (literature)
10-20 per million adults
<15 years 6 per millionOver 15 years 4.4 per million
HA data (2003-2008 Oct 15)
-
Total number during the period<15 years: 19 cases (2-7 per year)>=15 year: 279 cases (43-56 per year)
Average Incidence7.4 per million
AFP data (age<15y) -
2004: 2 cases (1.99 per million)2005: 8 cases (8.25 per million)2006: 3 cases (3.19 per million)2007: 2 cases (2.17 per million)2008: 1 case (1.11 per million)Average: 3.20 cases (3.34 per million)
After flu vaccination1-2 per million vaccinated
Not available
Summary
• Epidemiology of HSI in HK is in general agreement with global picture (low case fatality ratio real or artifact?)
• Recent data shows HSI probably peaked late September
• Timing and severity of ‘second wave’ uncertain
• School closures seemed to have delayed transmission, but outbreaks returned once school re-opened
• Local epidemiological data supports target groups for HSI vaccination, including persons with underlying medical conditions, young children, elders, HCW