Influenza B infections in children: A review

Table 1 The differences between influenza A and influenza B illness in children[2,13-16]

Variables	Influenza A	Influenza B
Epidemiology	Constitutes about 75% of total influenza	Constitutes about 25% of total influenza
Epidemic/pandemic	Causes both epidemics and pandemics	Causes epidemics
Epidemic peak1
Southern hemisphere	July-September	August-September
Northern hemisphere	January-February	February-March
Virology
Family	Orthomyxoviridae	Orthomyxoviridae
Type	Single-strand RNA virus	Single-strand RNA virus
Subtypes/lineages	18 H subtypes and 11 N subtypes	Two lineages: B (Victoria) and B (Yamagata)
Common types	A(H1N1) and A(H3N2)	Victoria and Yamagata lineages
Pandemic strain	A(H1N1) pdm09 virus	/
Infection	Humans, pigs, horses, wild birds, etc.	Only in humans (possibly in seals)
Host factors (children)[13]
Age (yr) (median)	2.0	4.2
Infants	Commonly affected	Less commonly affected
School-age	Can be affected	Commonly affected
Gender	Male predilection	Male predilection
Clinical features[13,16]
Fever	High	< 38.5 °C
Febrile convulsion	About 5.4%	About 10.7%
Rhinorrhea	Common	Common
Underlying medical conditions	Not so common (26%)	More common (34%)
Length of hospital stay (median)	5 d	3 d
Gastrointestinal symptoms (abdominal pain, vomiting, diarrhea)	Less common	More common
Myositis	1.1%-6%	4.5%-15%
Otitis media	26%	19%
Laboratory parameters
Leucopenia	Less common (8%)	More common (19%)
Leucocytosis	8%	7%
Elevated CRP	31%	15%-46%
Treatment
Oseltamivir	Effective	Effective
Zanamivir inhalation	Effective in ≥ 5 yr of age	Effective in ≥ 5 yr of age
Prognosis	Good	Good
Complications	May occur	In young children/having comorbidities
Vaccine (Quadrivalent)	Effective	Effective

¹Exceptions do occur in some countries.