Table. Neutralizing antibody titers for convalescent-phase serum samples from 25 patients with SFTS, Yiyuan County, Shandong, China, 2011–2014*.

Patient no.	Titer by PRNT50
	First year	Second year	Third year	Fourth year
1	640	NT	320	80
2	80	NT	40	80
3	NT	NT	40	40
4	20	NT	40	40
5	20	NT	40	40
6	80	NT	80	20
7	40	NT	80	40
8	5	NT	20	40
9	40	NT	40	20
10	160	NT	80	80
11	160	NT	20	80
12	160	NT	40	40
13	40	NT	20	NT
14	NT	NT	320	NT
15	160	NT	160	80
16	320	NT	40	40
17	160	NT	40	40
18	NT	NT	80	40
19	640	NT	160	160
20	320	80	80	NT
21	640	320	80	NT
22	20	20	20	NT
23	320	80	NT	NT
24	NT	80	40	NT
25	640	80	160	NT

*Convalescent-phase serum samples were obtained during the first, second, third, and fourth years after discharge of the patients from the hospital. NT, no test performed because serum was not available; PRNT₅₀, plaque reduction neutralization test indicating the serum titer that reduced 50% of plaque-forming units of SFTS virus; SFTS, severe fever with thrombocytopenia syndrome.