Measles
Introduction
- Measles:
viral illness → ไข้, malaise, rash, cough, coryza, conjunctivitis
- Highly
contagious →
attack rate 90% ในผู้ที่ไม่มีภูมิคุ้มกัน
- เป้าหมาย: global eradication (host เฉพาะมนุษย์,
มี vaccine ที่มีประสิทธิภาพ)
แต่ยังไม่สำเร็จเพราะ
- vaccine
hesitancy
- ความขัดแย้งทางสังคม/การเมือง
- coverage
ต่ำจาก COVID-19 disruption
- ปัจจุบันยังมี outbreaks เพิ่มขึ้นทั่วโลก
Epidemiology
- Incidence:
ยังคงเป็นสาเหตุการเสียชีวิตสำคัญในเด็ก < 5 ปี โดยเฉพาะประเทศ low vaccine coverage
- ก่อน vaccine (1960s) →
> 2 ล้านตาย/ปี
- Vaccine
→ ลด incidence
และ mortality อย่างชัดเจน
- Global
burden:
- 2000–2016
→ ลด measles
incidence 87% และ mortality 84%
- แต่ 2019 →
> 207,000 deaths (สูงสุดในรอบ 20 ปี)
- 2020–2023
→ cases ลดลงช่วง COVID-19 แต่กลับขึ้นอีก (663,795
cases ในปี 2023)
- High-risk
groups:
- เด็กเล็กที่ยังไม่ได้ vaccine
- ผู้ไม่ได้ฉีด vaccine (medical, social, hesitancy)
- ผู้ได้เพียง 1 dose (ยัง fail ~5–10%)
- ผู้ที่ vaccine failure (rare, 2-dose efficacy ~97–99%)
- Maternal
antibody: เด็กที่แม่ได้ vaccine (ไม่ใช่
natural infection) →
maternal Ab titer ต่ำกว่า → immunity
หายไวกว่า (< 12 เดือน risk สูงขึ้น)
Transmission
- Airborne
& droplets: อยู่ในอากาศได้ < 2 ชม.
- Attack
rate: ~90% ใน susceptible contacts
- Period
of infectivity:
- 5 วันก่อน rash →
4 วันหลัง rash
- Max
contagious → late
prodrome (ไข้ + respiratory symptoms)
- Incubation:
6–21 วัน (median 13)
- Transmission
reported:
- Air
travel, airports
- School
& dense communities
- Seasonality:
temperate → late
winter–early spring; tropical →
year-round
Protective Immunity
- Natural
infection →
lifelong immunity
- Vaccine
→ effective, two doses
essential
- 1
dose: 93–95% protection
- 2
doses: > 97% protection
- Outbreak
data: unvaccinated risk สูงกว่าผู้ฉีด vaccine >
200 เท่า
- Maternal
HIV infection →
transplacental Ab ต่ำ → เด็กติดเชื้อเร็วขึ้น
Measles Control & Global Status
- Herd
immunity threshold: > 95% coverage เพื่อหยุด transmission
- WHO/UNICEF
initiatives (2000–2030): ป้องกัน ~57 ล้าน deaths (2000–2022)
- Global
coverage:
- MCV1:
จาก 72% (2000) →
86% (2019) → ลดเหลือ 81% (2021, COVID disruption) → 83% (2023)
- MCV2:
จาก 18% (2000) →
74% (2023)
- Regional
status:
- Americas:
elimination achieved (2002), แต่ยังมี outbreaks จาก importation
- USA:
endemic eliminated (2000) →
outbreaks from undervaccinated groups (2019: 1282 cases, highest since
1992)
- Canada:
eliminated (1998) →
outbreaks จาก importation (2011 Quebec 725 cases)
- Europe:
resurgence หลัง 2018 (Ukraine > 53,000 cases)
- Africa:
ยัง burden สูงสุด (2019 > 600,000
cases)
- Asia
(SEAR & WPR): progress, แต่ India และ Philippines ยัง burden สูง
- Eastern
Mediterranean: conflict & poor health systems → ongoing outbreaks
Clinical/Public Health Pearls
- Extremely
contagious: airborne + crowding = explosive outbreaks
- Most
deaths: malnourished children, resource-limited settings
- Prevention:
only via vaccination, 2 doses mandatory
- COVID-19
impact: ~40M children missed measles vaccine dose (2021) → global resurgence
- Outbreak
definition (CDC): > 3 epidemiologically linked cases
- Control
measures: rapid vaccination of susceptible contacts, strict outbreak
response
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✅ Key Points for Clinicians
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Clinical Manifestations, Diagnosis & Management
Introduction
- Measles:
viral illness, contagious มาก (attack rate ~90% ใน susceptible individuals)
- Contagious:
5 วันก่อน rash → 4 วันหลัง rash
- Clinical
spectrum:
- Classic
measles (immunocompetent)
- Modified
measles (partial immunity, milder)
- Atypical
measles (killed vaccine recipients, severe pneumonitis)
- Neurologic
syndromes: ADEM, SSPE
- Severe
measles: immunocompromised →
giant cell pneumonia, MIBE
- Complications:
secondary infection, pneumonia, encephalitis
Clinical Manifestations
Stages of infection
- Incubation:
6–21 วัน (median 13), asymptomatic
- Prodrome
(2–4 วัน): fever, malaise, anorexia, conjunctivitis,
coryza, cough
- Koplik
spots: enanthem 1–3 mm whitish lesions, pathognomonic, appear ~48 hr
before rash
- Exanthem:
erythematous, maculopapular rash →
cephalocaudal, centrifugal spread
- blanching
early → non-blanching
later
- ±
petechiae, hemorrhagic in severe cases
- lasts
6–7 วัน → fades in order of appearance, ± desquamation
- Recovery:
fever resolves; cough อาจ persist 1–2 wk
Variants
- Modified
measles: mild, long incubation, not highly contagious
- Atypical
measles: high fever, rash starts on extremities (palms/soles
included), pneumonitis, severe
Complications (≈30% cases)
- GI:
diarrhea (8%), stomatitis, hepatitis
- Pulmonary:
pneumonia (6%, most common cause of death), croup, bronchiolitis,
bacterial superinfection (S. pneumoniae, H. influenzae, S. aureus, GAS),
post-measles bronchiectasis
- Neuro:
- Encephalitis
(1:1000, 25% sequelae, 15% fatal)
- ADEM
(acute disseminated encephalomyelitis): 1:1000, post-infectious, 10–20%
mortality, sequelae common
- SSPE
(subacute sclerosing panencephalitis): 7–10 yr post-infection,
progressive fatal, ↑
risk if infected < 2 yr
- Ocular:
keratitis, corneal ulceration →
blindness
- Cardiac:
myocarditis, pericarditis
- Immune
suppression: post-measles "immune amnesia" → loss of prior humoral
immunity, secondary infections
Groups at Risk
- Immunocompromised
(AIDS, malignancy, transplant, immunosuppressive drugs) → giant cell pneumonia, MIBE (measles inclusion body encephalitis)
- Pregnant
women → maternal
mortality, pneumonia, encephalitis, miscarriage, IUFD, preterm birth
- Malnourished,
vit A deficiency →
severe disease, ocular complications
- Infants,
elderly → higher
morbidity/mortality
Diagnosis
- Clinical
suspicion: febrile rash + cough + coryza + conjunctivitis
- Labs:
- IgM:
positive ~day 3 of rash (up to 30 days)
- IgG
seroconversion: > 4-fold rise
- RT-PCR
(blood, NP swab, urine): confirmatory, high sensitivity
- Culture:
not routine, used for epidemiology
- Differential
diagnosis: dengue, rubella, roseola, parvovirus B19, enterovirus,
varicella, GAS scarlet fever, drug eruption, meningococcemia, RMSF, EBV,
Mycoplasma, Kawasaki, MIS-C
Treatment
- Supportive:
antipyretics, fluids, treat bacterial infections
- Vitamin
A: ↓
morbidity/mortality esp. children < 2 yr, malnourished, hospitalized
- <
6 mo: 50,000 IU PO daily ×2 days
- 6–11
mo: 100,000 IU ×2 days
- >
12 mo: 200,000 IU ×2 days
- Severe
deficiency (xerophthalmia, Bitot spots) →
repeat dose at 4–6 wk
- Ribavirin:
consider in severe pneumonia (infants, immunocompromised, ventilated pts);
evidence limited
- Investigational
for SSPE: isoprinosine, IFN-α
(transient effect, no cure)
Prevention
- MMR
vaccine:
- 2
doses essential (1st: 9–12 mo, 2nd: 15–18 mo or school entry depending on
schedule)
- Herd
immunity > 95%
- Post-exposure:
- MMR
vaccine < 72 hr
- IVIG
< 6 days for high-risk (infants, pregnant, immunocompromised)
- Infection
control:
- Airborne
precautions: 4 วันหลัง rash onset (longer in
immunocompromised)
- Susceptible
exposed individuals: exclude day 5–21 post-exposure
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✅ Key Clinical Practice Points
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