MAEH Seminar 17 Feb 2021 (Dr Amir)

WEBINAR MAEH

Understanding COVID-19 Series:
The Infectivity Period and more.....

DR. MUHAMMAD AMIR KAMALUDDIN
MAEH EXCO 2019-2021

1

WEBINAR MAEH

UNLIMITED COVID-19 SERVICES :
THE INFECTIVITY PERIOD & MORE…

For Environmental Health(EHO & AEHO) in Malaysia

17th February 2021 | 8.30 PM
LIVE FB

MALAYSIAN ASSOCIATION OF Moderator Speaker
ENVIRONMENTAL HEALTH (MAEH)
Mr Megat Azman Megat Mokhtar Dr Muhammad Amir Kamaluddin
Vice President of MAEH MAEH Committee Members/
Former Head of EHRC, IMR

SUGGESTED REGULAR READINGS

• http://covid-19.moh.gov.my
• https://www.who.int/emergencies/diseases/novel-coronavirus-2019
• https://www.cdc.gov/coronavirus/2019-ncov/index.html
• https://www.worldometers.info/coronavirus/

3

INTRODUCTION • Malaysia 31 Jan 2021
• **Pop: 32.7 million
• The virus: SARS-CoV-2 • Cases: 214,959
• The disease: COVID-19 • Deaths: 760
• First case: Early Dec 2019 • Incidence: 0.66%
• First case in Malaysia: 25 Jan • CI 66 cases per 10,000 pop
• CFR: 0.36%
2020
• *First Malaysian: 4 Feb 2020

*Asita Elengoe. Osong Public Health Res ** Estimated Malaysia pop 2020 (Stats Dept Malaysia)
Perspect. 2020 Jun; 11(3):93-1000
4

• 3 Jan 2021, • Rt
• measure of contagiousness
• MOH announced

• Rt of 1.11 (95% CI 1.09–1.12).

• On 28 December 2020, the MOH
reported that 89% of COVID-19
patients in Malaysia were
asymptomatic or displayed mild
symptoms

5

6

SITUATIONAL ANALYSIS

7

8

9

10

PRIMARY PREVENTION

• Mask
• Hand hygiene
• Social / physical distancing
• PPE

11

TRANSMISSION mode

• Respiratory droplets are >5-10 μm in diameter whereas droplets <5μm
in diameter are referred to as droplet nuclei or aerosols.

• Respiratory droplet transmission can occur when a person is in close
contact (within 1 metre) with an infected person who has respiratory
symptoms (e.g. coughing or sneezing) or who is talking or singing; in
these circumstances, respiratory droplets that include virus can reach
the mouth, nose or eyes of a susceptible person and can result in
infection.

WHO: Scientific Brief 9 July 2020; Transmission of SARS-CoV-2: implications for infection prevention precautions

12

TRANSMISSION MODES

• contact • The primary predominant mode
• droplet of transmission is by droplet.
• airborne
• fomite
• fecal-oral
• bloodborne
• mother-to-child
• animal-to-human transmission.

13

ASYMPTOMATIC TRANSMISSION

• A recent systematic review estimated that the proportion of truly
asymptomatic cases ranges from 6% to 41%, with a pooled estimate of
16% (12%–20%).

• One study of transmission in Singapore reported that 6.4% of secondary
cases resulted from pre-symptomatic transmission.

• One modelling study, that inferred the date of transmission based on the
estimated serial interval and incubation period, estimated that up to 44%
(25-69%) of transmission may have occurred just before symptoms
appeared.

• Estimates from modelling studies differs from available empirical data

WHO: Scientific Brief 9 July 2020; Transmission of SARS-CoV-2: implications for infection prevention precautions

14

TRANSMISSION RISK • higher rates of transmission
among symptomatics
• age group
• viral load (ct)
• crowded
• confined space
• close conversation
• prolonged contact

15

ACTIVITIES

• Limit close contact between infected people and others is central to breaking
chains of transmission of the virus causing COVID-19.

• Identify suspect cases as quickly as possible,
• Testing, and isolating suspected cases.
• Identify all close contacts of cases so that they can be quarantined.
• By quarantining close contacts, potential secondary cases will already be

separated from others before they develop symptoms or they start shedding
virus if they are infected, thus preventing the opportunity for further onward
spread.
• The incubation period of COVID-19, which is the time between exposure to
the virus and symptom onset, is on average 5-6 days, but can be as long as
14 days.
• Thus, quarantine should be in place for 14 days from the last exposure to a
confirmed case. (now 10 days)

16

SYMPTOMS

3 classic early symptoms 7 other signs & symptoms
• fever, • Sore throat
• dry cough • Muscle aches and joint pain
• loss of sense of smell and taste. • Diarrhoea
• Conjunctivitis
Get yourself tested • Headache
• Skin rash
• Discolouration of fingers or toes

17

TRANSMISSION RISK (APPROACH WITH CAUTION)

• 0-9 years: 1.2% • Older adults are more vulnerable
• 10-19 years: 9.9% to the virus but less likely to
• 20-34 years: 28.3% spread it to others.
• 35-49 years: 35.1%
• 50-64 years: 19.1% • Adults between 20 to 49 years
• 65-79 years: 5.6% contributed to 65% of cases
• 80+ years: 0.6%

M. Monod et al., Science (2 Feb 2021).

18

CASE DETECTION

• Case definition • Health screening

• Disease surveillance • At port of entry
• Mandatory foreign worker’s (fr Jan 1
• ACD / PCD
2021)
• Syndomic surveillance
• Quarantine Vs Isolation
• ILI
• SARI

• Laboratory surveillance (SIMKA)

19

CASES • KKM DG: about 89% Covid-19
patients in Malaysia are asymptomatic
Clinical stages 1-5 or showing mild symptoms. (NST 28
Dec 2021)
Asymptomatic
Presymptomatic 20
Symptomatic

Mild
Moderate
Severe

HOW LONG DOES IT TAKE TO GET SICK ?

• The incubation period for COVID-19, which is the time between
exposure to the virus (becoming infected) and symptom onset, is on
average 5-6 days, however can be up to 14 days.

• During this period, also known as the “pre- symptomatic” period, some
infected persons can be contagious. Therefore, transmission from a pre-
symptomatic case can occur before symptom onset.Apr 2, 2020.
Coronavirus disease 2019 (COVID-19)www.who.int › docs › 20200402-
sitrep-73-covid-19

• On average it takes 5–6 days from when someone is infected with the
virus for symptoms to show, however it can take up to 14 days.

21

HOW LONG ARE YOU INFECTIOUS?

• The “infectious period” means the time one is easily able to spread
the virus

• The most infectious period is 1 to 3 days before symptoms start, and
in the first 7 days after symptoms begin.

22

Summary: IP, infectivity period, quarantine

• IP = 5-6 days
• max IP 14 days
• Risk low after 10 days
• Shortest quarantine is 7 days with -ve exit test (France)

• mild to moderate: infectious for 10 days after DOO (CDC; October 19,
2020)

23

ASYMPTOMATICS

• Analytical model of multiple • Never symptomatic: 24%
scenarios of proportions of • Presymptomatic: 43%
asymptomatic individuals with • Symptomatic: 33%
COVID-19 and infectious periods.

• Transmission from asymptomatic
individuals was estimated to
account for more than half of all
transmissions.

Michael A. Johansson et al., SARS-CoV-2 Transmission From People Without COVID-19 Symptoms. JAMA Network
Open. 2021;4(1):e2035057. doi:10.1001/jamanetworkopen.2020.35057

24

TEST POSITIVITY RATE

• WHO recommends that all suspected cases be tested for COVID-19
according to WHO case definitions.

• Improve national testing capacity, as needed, and assess the
effectiveness of the laboratory network.

• Intensify investigation of cases and clusters and SARI/ILI surveillance.
• When clusters become large, it is critical that testing of suspected

cases continues so that cases can be isolated, contacts can be
quarantined, and chains of transmission can be broken.
• 5% positive rate (1 positive in 20 or 30 tested)

25

26

27

ENDING ISOLATION

• Studies have not found evidence that clinically recovered persons
with persistence of viral RNA have transmitted SARS-CoV-2 to others.

• These findings strengthen the justification for relying on a symptom
based, rather than test-based strategy for ending isolation of these
patients, so that persons who are by current evidence no longer
infectious are not kept unnecessarily isolated and excluded from work
or other responsibilities. (CDC Oct 19, 2020)

• For most persons with COVID-19 illness, isolation and precautions can
generally be discontinued 10 days after symptom onset and
resolution of fever for at least 24 hours, without the use of fever-
reducing medications, and with improvement of other symptoms.

28

WHO: Break transmission chain

• Identify and test suspected cases
• Isolate cases.
• Trace all close contacts of infected cases
• Quarantined contacts.
• The IP (exposure date to onset date), average 5-6 days, but can be as long as 14

days.
• Thus, quarantine for 14 days (now 10 days) from the last exposure to a

confirmed case.

• The question is how infective is the case
• Viral load Ct value

WHO: Scientific Brief 9 July 2020

29

POSITIVITY RATE

• Percentage of those who are identified as infected out of those
tested.

• The World Health Organisation (WHO)’s recommendation is 5 per
cent and below whereas our testing positive rate registered 8.9 per
cent as of January 3, 2021.

• A rate higher than 5% would suggest or imply a R0 that’s speeding up

Recalibrating The Covid-19 Containment Strategy — Jason Loh By CodeBlue | 03 February 2021
There is a need for the government to listen to experts and professionals by re-thinking its Covid-19 containment
strategy.

https://codeblue.galencentre.org/2021/02/03/recalibrating-the-covid-19-containment-strategy/ 30

TESTS ACCURACY

• Sn: the ability of a test to correctly identify patients with a disease.
• Sp: the ability of a test to correctly identify people without the disease.
• RTK Ag
• RT-PCR

31

Annex 4c
GUIDELINE ON COVID-19 TESTING USING ANTIGEN RAPID TEST KIT (RTK-Ag)
FOR THE HEALTH FACILITIES, MINISTRY OF MALAYSIA VERSION 3.0; 22nd May 2020

• RTK-Ag has the advantage of detecting COVID-19 outbreaks quickly and
in large quantities. Malaysia has been using RTK-Ag since 6th May 2020.
The RTK-Ag used has undergone re-evaluation by the IMR and the
results are satisfactory and within the Ministry of Health’s (MOH)
minimum sensitivity and specificity values.

• Limit of detection for RTK-Ag is currently at Cycle Treshold (Ct) value of
30. Any Ct value above 30 is unable to be detected by RTK-Ag. Ct value
of 30 is equivalent to about 300-400 viral copy numbers on the
Nasopharyngeal Sample (NPS). As compared to RT-PCR, it involves
amplification step and it’s limit of detection is about 4-5 viral copy
numbers

32

ISSUES

• Mutation and virus variants
• Re-infection with variant virus SARs-CoV-2 ?
• Impact on vaccine efficacy
• Adverse effect of vaccine

COVID-19 media briefing - Monday 08 February, 2021 : WHO DG’s Statement

33

WHO DG: 5 Feb 2021 - on vaccine

• 130 countries, with 2.5 billion people, were yet to administer a single
dose.

• More than 90% of the countries now rolling out vaccines are high- or
upper-middle income countries.

• Seventy-five percent of doses have been deployed in only 10
countries.

34

Terima Kasih

35

Replication-competent virus

• Concentrations of SARS-CoV-2 RNA measured in upper respiratory specimens
decline after onset of symptoms

• The likelihood of recovering replication-competent virus also declines after
onset of symptoms.

• For patients with mild to moderate COVID-19, replication-competent virus
has not been recovered after 10 days following symptom onset.

• Recovery of replication-competent virus between 10 and 20 days after
symptom onset has been documented in some persons with severe COVID-19
that, in some cases, was complicated by immunocompromised state.
However, in this series of patients, it was estimated that 88% and 95% of their
specimens no longer yielded replication-competent virus after 10 and 15 days,
respectively, following symptom onset.

https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html
36

• Sensitivity, defined as the probability that a test result will be positive when
the disease exists (true positive rate) was calculated as = VP/(VP + FN).

• Specificity, defined as the probability that a test result will be negative when
the disease is not present (true negative rate) was calculated
as = VN/(VN + VP).

• The PLR is the ratio between the probability of a positive test result given the
presence of the disease and the probability of a positive test result given the
absence of the disease, that is = true positive rate/false positive rate, or
expressed as sensitivity/(1-specificity).

• The NLR is ratio between the probability of a negative test result given the
presence of the disease and the probability of a negative test result given the
absence of the disease, that is = false negative rate/true negative rate, or
expressed as (1-sensitivity)/specificity.

37

• Individuals who have tested positive have been hospitalized in
isolation

• Those who have tested negative quarantined for 14 days at
centralized facilities and then retested on day 13.

• We assessed the proportion of international entrants to China with
asymptomatic SARS-CoV-2 infection.

38

PERSATUAN KESIHATAN ENVIRONMEN MALAYSIA
(MALAYSIA ASSOCIATION OF ENVIRONMENTAL HEALTH)

NO. 29-2 JALAN EQUINE 1A
TAMAN EQUINE

43300 SERI KEMBANGAN
SELANGOR

DARUL EHSAN