Diseases / List of Viral Diseases / West Nile Virus Disease / Detailed Disease Description:

< > Literature Reports of INCUBATION PERIOD for West Nile Virus Disease:

Incubation Period

Editorial Overview (Editorial Overview Text Replicated on Overall Disease page - West Nile Virus Disease)
  • The incubation period is usually fairly short and may vary between species.
  • In humans the incubation period is recorded within the range of 1 to 15 days, more usually 3 to 6 days.

(J39.84.w1, J71.54.w1, J71.75.w1, J84.5.w2, J84.7.w20, J84.8.w4, J88.36.w1, J100.93.w1, J101.86.w2, J116.5.w1, J120.20.w1, J120.20.w1, J122.77.w1, J123.31.w1, J127.46.w1, J129.42.w1, J133.951.w9, J133.951.w12, B241.49.w49, P32.1.w13, B240.14.w14, B243.31.w1, W170.Nov01.WNV2, N7.51.w3)

Source Information

Species-specific Incubation Period:

Corvus brachyrhynchos - American Crow:

  • Deaths at five to eight days after subcutaneous inoculation with a New York 1999 strain of WN virus. (J133.951.w9)
Equus caballus - Domestic horse:
  • Nervous signs in one of four horses infected experimentally, beginning 58 days after inoculation. (P32.1.w13)
  • Development of neutralizing antibodies by 7-11 days post-infection (J133.951.w37)
  • Fever and neurological signs in one of twelve horses infected experimentally by mosquito bite, beginning eight days after infection. (J84.8.w4)
Homo sapiens - Human:
  • One to six days. (B240.14.w14, B243.31.w1)
  • Three to six days. (J84.5.w2, J129.42.w1)
  • About three days. (J100.93.w1)
  • Five to fifteen days. (J123.31.w1)
  • Usually three to 15 days. (W170.Nov01.WNV2)
  • Following transplantation of organs from a WN virus-infected donor, illness onset occurred at 7-17 days after transplantation. (N7.51.w3)
  • Following blood transfusion, illness onset as soon as three days later in one patient and one day after transfusion in another patient. (N7.51.w3)
Macaca rhesus - Rhesus macaque (Cercopithecidae - Old-world monkeys (Family)):
  • Seven to eight days to the development of fever. (J71.75.w1)
  • Five to eight days following intracerebral inoculation. (J120.20.w1)
Chlorocebus aethiops - Savanna monkey:
  • Fever after 6-7 days following inoculation. (J120.20.w1)
Macaca radiata - Bonnet macaque (Cercopithecidae - Old-world monkeys (Family)):
  • Signs from eight days following intranasal inoculation. (J88.36.w1)
Mus domesticus - Laboratory mouse:
  • Death in two to five days following intracerebral or intraperitoneal inoculation of two to four day old mice. (B241.49.w49)
  • 1-2 day old, intracerebral, intraperitoneal or subcutaneous inoculation fatal, with an incubation of 3-4 days, 4-5 days and 5-6 days respectively. Smaller dose required for lethal effect if given intracerebrally. WN virus strain isolated from a rook in  Ukraine, 1980. (J116.5.w1)
  • 3-4 week old. Intracerebral inoculation resulting in paralysis and death after an incubation period of 4-5 days, but no signs following intraperitoneal or subcutaneous inoculation. WN virus strain isolated from a Corvus frugilegus - Rook in the Ukraine, 1980. (J116.5.w1)
  • Two months old. Intracerebral inoculation resulting in paralysis in 20%; no signs following intraperitoneal or subcutaneous inoculation. WN virus strain isolated from a Corvus frugilegus - Rook in the Ukraine, 1980. (J116.5.w1)
  • Strain AN-1230 from a sick Columba livia - Rock pigeon in Egypt. Initial inoculation into day-old mice resulted in paralysis of 1/7 mice after seven days. Passage of brain suspension into two-day-old mice resulted in paralysis and death on the third and fourth days post-inoculation. Passage of brain suspension from these individuals inoculated into three-day-old and three-week-old mice resulted in paralysis and death by the fifth day post inoculation. (J39.84.w1)
  • Adult mice, susceptible by intracerebral route and with higher titre virus by intraperitoneal route; signs of encephalitis. Newborn mice found to be equally susceptible to intracerebral or intraperitoneal inoculation. Egypt strain, 1950 (J122.77.w1)
  • Aerosol exposure resulted in notable titres of virus in the lungs by 24 hours, in blood and other tissues (including the brain) by 48 hours, and specific signs of disease from four days. (J127.46.w1)
  • No infection occurred following the application of very large doses of WN virus to mice via the skin or eyes or by mouth. (J127.46.w1)
  • Intratracheal inoculation resulted in viraemia within 24 hours. (J127.46.w1)
  • Intranasal inoculation resulted in viraemia by 96 hours. (J127.46.w1)
  • Ingestion of virus resulted in virus detected in the brain by three days after infection but viraemia and detection in other tissues only after five days; it was suggested virus particles may have reached the brain via diffusion of virus particles into the olfactory bulbs. (J71.54.w1)
  • "Signs of encephalitis appeared 2 to 8 days after intracerebral inoculation, depending on the virus dose and on the host [age and species i.e. rat or mouse]". (J101.86.w2)
  • Longer incubation period and more variation in the incubation period between individuals, in animals with more resistance to lethal infection. (J101.86.w2)
  • Longer incubation period and longer time to death following intracerebral inoculation of smaller doses of virus compared with inoculation of higher doses. In one to three day old mice, Egypt 101 WN virus strain. (J101.86.w2)
  • First signs day six or seven following intraperitoneal inoculation. (J133.951.w12)
Mesocricetus auratus - Golden Hamster:
  • Six days to first signs following intraperitoneal inoculation of adult hamsters with a USA strain from 1999. (J84.7.w20, J91.65S3.w2)

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Authors & Referees

Authors Debra Bourne (V.w5)
Referee Suzanne I. Boardman (V.w6); Becki Lawson (V.w26)

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