Table 1.

Clinical presentation and serological response of the index patient and her symptomatic contacts

	Age (years), sex	Date of illness	Symptoms	Haemagglutinin inhibition titres*
				First serum†	Second serum‡
Patient	20, female	May 5	Fever, cough, sore throat, shortness of breath	40	80
Brother	17, male	Apr 24	Rhinorrhoea, sore throat	<10	<10
Neighbour	83, female	Early May§	Cough, sore throat, headache	<10	<10
Nurse in hospital A¶	34, female	May 8	Fever, rhinorrhoea, cough, sore throat, tinnitus, muscle ache	<10	<10
Mother	45, female	May 11	Fever, cough, sore throat	<10	<10
Boyfriend	31, male	May 14	Fever, rhinorrhoea, sore throat	<10	<10
Physician in hospital B	40, male	Mid May§	Sore throat, muscle ache	10	<10

^*Established by use of turkey red blood cells. Titres are reported as the reciprocal of the highest dilution of serum that inhibited virus-induced haemagglutination.

^†Obtained on May 24 except for her boyfriend, who received the first serological test on May 25.

^‡Obtained on June 8.

^§Exact date of illness onset not available.

^¶The registered nurse's two children developed influenza-like illnesses 1 day before her illness. She declined to have her children tested for influenza infection.