CHAPTER 2 AIR/DROPLET- BORNE DISEASES

CHAPTER 2

AIR/DROPLETBORNE DISEASES

Airborne transmission occurs by dissemination of suspended particles five micrometres or smaller in diameter. Droplets can be formed when a person coughs, sneezes or talks, or during administration of drugs via nebuliser or invasive procedures such as suctioning and bronchoscopy, and transmission occurs when they are propelled a short distance (within a metre) through air and deposited on the host's mucous membranes.

14

HAEMOPHILUS INFLUENZAE TYPE B DISEASE

23

MENINGOCOCCAL INFECTION

30

RUBELLA

15

HAND, FOOT AND MOUTH DISEASE

24

MUMPS

32

VIRAL CONJUNCTIVITIS

17

INFLUENZA

25

PERTUSSIS

32

CHICKENPOX

13

20

MEASLES

27

PNEUMOCOCCAL DISEASE

microorganisms generated from infected persons are propelled a short distance (within a meter) through air and deposited on the host's mucous membranes (such as conjunctiva, nasal mucosa, mouth or respiratory tract).

HAEMOPHILUS INFLUENZAE TYPE B DISEASE

HAEMOPHILUS INFLUENZAE TYPE B DISEASE

Haemophilus influenzae type b (Hib) is a bacterium (gram--negative coccobacillus) that causes severe illnesses such Haemopahs i plunseuinmflouneinaz, abeacttyepraeebm(iaH iabn)di smaenbiangcitteisr.i u Tmhe( gmraodme- noef gtraatnivsemcisosciocno bisa bcyil l uinsh)atlhataiot nc a ouf s respsireavtoerye dilrlnoepslestes s ors uch as pneudmiroenctia c,obnatacctte wraiethm rieaspainradtomrye ntriancgti tsiesc.rTehtieonms oodf einfoefcttreadn psemrsisosniso.n Hiisb bdiyseinahsea lias tvioacncionfer--epsrepvireanttoarbyled.r o plets or direct contact with respiratory tract secretions of infected persons. Hib disease is vaccine-preventable.

In 2016, there were two cases of Hib disease reported compared to three cases in 2015 (Figure 2.1). The two cases In 2016,wtehreer elabwoeraretotrwy-o-cocnafsiremseodf wHitibh pdoisseitaivsee brleopoodr cteudltucroems. pTahree tdwtoo stehpraereatcea csaessesi n w2e0re1 5ag(eFdi g ounree y2e.a1r) .anTdh e58t w yeoacrsa ses were labreosrpaetoctriyv-eclyo,n afinrmd ewderwe i othf Mpoaslaityiv eethbnloicoitdy c(Tualbtulere 2s..1 T ahned t2w.2o). s Tehpea trwatoe ccaasesse swewree r celaassgiefidedo anse inydeiagernaonuds c5a8seyse ars respecti(vTealbyl,ea 2n.d3)w. ere of Malay ethnicity (Table 2.1 and 2.2). The two cases were classified as indigenous cases (Table 2.3).

Figure 2.1 Weekly distributionF oigf urerpeo2rt.1ed Hib cases, 2015--2016 Weekly distribution of reported Hib cases, 2015-2016 No. of cases 3

2

1

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Week 2015 2016

TTaabbllee 22..11

Age-geAnged-e-grenddisetrr dibisutrtiibountiaonn d anadg aeg-se-p-sepcecifiifcic i inncciiddeennccee rartaet eofo rfepreoprtoerdt eHdibH caibsecsa, 2s0e1s6, 2016

AAggeeg grroouupp 0-4

MMaallee 1

FFeemmaallee 0

TToottaall 1

%%

InIcnicdideennccee rraattee ppeerr 101000,0,00000p pooppuullaattiioonn**

50

0.4

5 -01--44

01

00

01

500

00..04

155---1244

00

00

00

00

00..00

2155--3-244

00

00

00

00

00..00

3255--4-344

00

00

00

00

00..00

4355--5-444

00

00

00

00

00..00

5455--6-544

10

00

10

500

00..20

5655--+64 To65ta+l Total

01

00

01

500

00..02

20

00

20

1000

00..00

2

0

2

100

0.0

*Ra*tReast(eSasro eaurrbec a besa:esSedidno gonan2 p 20o01r1e66 D eessettpiimmaraattmteeded nmmtiodid-f-y-Syeetaaart rpisoptipocupslu)altaiotino.n .

(Source: Singapore Department of Statistics)

Table 2.2 Ethnic-gender distribution and ethnic-specific incidence rate of reported Hib cases, 2016

Male Female

Total

%

Incidence rate per 100,000 population*

Singapore residents

Chinese

0

0

0

0

0.0

Malay

2

0

2

100

0.4

Indian

0

0

0

0

0.0

Others

0

0

0

0

0.0

Foreigners

0

0

0

0

0.0

Total

2

0

2

100

0.0

*Rates are based on 2016 estimated mid-year population. (Source: Singapore Department of Statistics)

14

Age group

0-4 5-14 15-24 25-34 35-44 45-54 55-64 65+ Total

Table 2.3 Total number of notifications* received for Hib, 2012-2016

2012

2013

2014

2015

Local Imported Local Imported Local Imported Local Imported

0

0

0

0

1

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

2

0

1

0

0

0

0

0

3

1

0

0

0

0

1

0

4

0

2

0

3

0

1

0

9

1

5

1

3

0

*Excluded tourists and foreigners seeking medical treatment in Singapore.

2016

Local Imported

1

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

2

0

HAND, FOOT AND MOUTH DISEASE

Hand, foot and mouth disease (HFMD) is a common childhood viral disease characterised by brief prodromal fever, followed by pharyngitis, mouth ulcers and rash on the hands and the feet. The disease is commonly mild and selflimiting. The common causative agents for HFMD are the coxsackieviruses type A, echovirus, and enterovirus A71 (EV-A71). HFMD can be transmitted from person to person through the faecal-oral or respiratory route.

A total of 42,154 cases of HFMD were reported in 2016, an increase of 49.4% compared to 28,216 cases reported in 2015 (Figure 2.2). There were no cases with severe complications due to HFMD reported in 2016.

The incidence rate was highest in the 0-4 years age group, with an overall male to female ratio of 1.2:1 (Table 2.4). Among the three major ethnic groups, Malays had the highest incidence rate, followed by Chinese and Indians (Table 2.5). No HFMD deaths were reported in 2016.

Viral isolation and PCR of EV 71 and other enteroviruses were carried out on samples collected at the KK Women's and Children's Hospital (KKH), National University Hospital and sentinel GP clinics. Of the isolates that were tested positive, the majority was coxsackieviruses type A (14.6%), followed by EV71 (0.6%). Among the coxsackieviruses, CA16 (38.8%) was the predominant serotype, followed by CA6 (32.0%).

WeeWkleyedkliys tdriisbtruibtiuotnioonf orFfe riFpgeigopuuorrrtereete 2d 2d..2H2 H F F MMDD ccaassees,s 2,021051--250-2106 1 6

No. of cases

1600

1400

1200

1000

800

600

400

200

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51

2015

2016

Week

Age group

0--4 5--14 15--24

Table 2.4

Age--gender distribution and age--specific incidence rate of reported HFMD^, 2016

Male

Female

Total

%

Incidence rate per

100,000 population*

14,722

11,948

26,670

63.3

11,453.9

6,009 753

4,642 710

10,651 115,463

25.3 3.5

2,290.7 197.1

Table 2.4 Age-gender distribution and age-specific incidence rate of reported HFMD^, 2016

Age group

Male

Female

Total

%

Incidence rate per 100,000 population*

0-4 5-14 15-24 25-34 35-44 45-54 55+ Total

14,722

11,948

26,670

63.3

6,009

4,642

10,651

25.3

753

710

1,463

3.5

755

941

1,696

4.0

758

550

1,308

3.1

153

114

267

0.6

54

40

94

0.2

23,204

18,945

42,149

100

^Excluded 5 tourists.

*Rates are based on 2016 estimated mid-year population. (Source: Singapore Department of Statistics)

11,453.9 2,290.7

197.1 133.8 130.5

35.3 15.6 751.7

Table 2.5 Ethnic-gender distribution and ethnic-specific incidence rate of reported HFMD^, 2016

Male

Female

Total

Incidence rate per

%

100,000 population*

Singapore residents

Chinese

15,522

12,873

28,395

67.4

971.4

Malay

3,670

2,962

6,632

15.7

1,261.1

Indian

863

709

1,572

3.7

440.5

Others

854

655

1,509

3.6

1,182.4

Foreigners

2,295

1,746

4,041

9.6

241.4

Total

23,204

18,945

42,149

100

751.7

^Excluded 5 tourists. *Rates are based on 2016 estimated mid-year population.

(Source: Singapore Department of Statistics)

Institutional outbreaks

There were 2,547 reported outbreaks of HFMD in 2016, each involving two or more cases. Table 2.6 gives a breakdown of HFMD outbreaks at various educational institutions by attack rate. One HFMD outbreak cluster is discussed below.

Since 2010, additional measures were introduced to curb the HFMD transmission in educational institutions. Childcare centres or kindergartens with prolonged HFMD transmission had their names published on the MOH website and were subsequently closed for ten days if disease transmission was prolonged for more than 16 days. These measures continued to be enforced in 2016 with public education enhanced.

Table 2.6 Outbreaks of HFMD in childcare centres/kindergartens, 2016

Attack rate (%) Childcare centres Kindergartens

50

-

-

Total

2,098

449

16

Outbreak at a Bedok childcare centre

An outbreak of HFMD involving 34 children aged between one and five years occurred between 18 February and 8 March 2016 in a childcare centre at Bedok. At the time of the outbreak, the centre had 19 full-time staff and 83 children in five classes: Infant, Nursery, Playgroup, Kindergarten 1 (K1) and Kindergarten 2 (K2).

The class-specific attack rates ranged from 15.4% to 57.9% (Table 2.7). The outbreak started with an infant who developed symptoms on 18 February 2016. The infection subsequently spread amongst other children. The last reported case was on 8 March 2016 (Figure 2.3).

Table 2.7 Attack rates of HFMD in a Bedok childcare centre,

18 February-8 March 2016

Class

No. enrolled

No. affected and attack rates

category Male

Female

Total

Male

% Female %

Total

%

Infant

9

6

15

3

33.3

2

33.3

5

33.3

Nursery

7

12

19

3

42.9

8

66.7

11

57.9

Playgroup 12

13

25

8

66.7

5

38.5

13

52.0

K1

4

7

11

1

25.0

2

28.6

3

27.3

K2

7

6

13

2

28.6

0

0.0

2

15.4

Total

39

44

83

17

43.6

17

38.6

34

41.0

Figure 2.3 Time distribution of 34 casFeisguorfe H 2.F3M D in a Bedok childcare centre,

Time distribution of 3148 caFseebs r ouf a HrFyM-8DM ina arc Bhed2o0k1 6childcare centre, 18 February--8 March 2016

9

Infant K1 K2 Nursery PG

8

7

6

5

4

3

2

1

0

No. of Cases

Date of Onset

INFLUENZA

INFLUENZA Influenza is an acute viral disease of the respiratory tract characterised by fever and symptoms such as sore throat, couIgnfhlu, ecnozray zisa a,nh aecaudtea c vhireal a dnisdeamsey oaflg tihae. rIet smpiaraytobrey tcroacmt p chlicaaratectderbisyedp nbey u femvoern aian,dp sayrmtipcutolamrsly suinchh aigs h s-orrisek thpraotaite,n ts such as cthoousghe, wcoitrhyzcao, h-meaodrabcidhieti easn.d I mt iysalsgpiar.e Iat dmafryo bme pcoemrspolnicattoedp ebrys ponneummaoinnliya, t pharortuicguhlairnlyfe inc t hioiguhs--rriesks ppiartaietonrtys sdurcohp lets and secarse ttihoonsse r weiletha csoe-d-mdourbriindgiticeos.u Igt hisi n spgraeandd fsronmee pzeinrsgo.n to person mainly through infectious respiratory droplets and

secretions released during coughing and sneezing. The causative agent is the influenza virus and three types of influenza virus (A, B, C) are recognised. The Influenza typeThAe vciarussaetsivein acgluednet itsw tohes iunbfltuyepnezsa ( vHir1uNs 1anadn tdhrHee3 N ty2p)etsh oaft iinnffleucetnhzau mviraunss (Aa,n Bd, hC)a avree b receongnaissseodc. iTahte d Inwfluitehnpzaa n demics andtywpeid eAs pvrireuasdese ipnicdleumdeic tsw. oIn fslubetnyzpaest y(pHe1NB1 i sanodc cHa3sNio2n) a tllhyata sinsfoeccita theudmwaniths arengdi ohnaavlee bpeideenm aicssso,caiantdedi n wfluitehn za type C ispaansdseomciacste adndw iwthidsepsopreaaddic ecpaidseems iacsn. d Inmfluineonrzalo tcyapleis eBd iso uoctbcraesiaoknsa.llDy iaasgsnoocisaitsedis wbiaths e rdegoionnathl eepcildineimcaiclsr,e acnodg nition of influinefnluzean-zliak etyipllen eCs is awsistohcoiartewdit hwoituht slapobroardaitco cryasceos n afnirdm matinioonr aloncdalissterda i onucthbareraakcst.e Driisaagtnioonsi.s is based on the clinical

recognition of influenza--like illness with or without laboratory confirmation and strain characterisation. In temperate and cold climates, influenza reaches peak incidence in winter. As the northern and southern Hemispheres have winter at different times of the year, there are two flu seasons each year: December--March in the Northern Hemisphere; and June--September in the Sou1th7ern Hemisphere.

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