[Emerging Infectious Diseases]
[Volume 4 No. 2 / April - June 1998]
Dispatches
Probable Human Infection with a Newly Described Virus in the Family
Paramyxoviridae
Kerry Chant,* Raymond Chan, Mitchell Smith,* Dominic E. Dwyer, Peter
Kirkland, and the NSW Expert Group 
*Public Health Unit, Sydney,
Australia; South Western Area Pathology Service, Sydney, Australia;
Institute of Clinical Pathology and Medical Research (ICPMR), Westmead,
Australia; and Elizabeth Macarthur Agricultural Institute, Menangle, New
South Wales, Australia
Stephen Conaty, NSW Department of Health; Yvonne Cossart, University of
Sydney; Gwendolyn Gilbert, ICPMR; Richard Jane, NSW Department of
Agriculture; Robert Love, University of Sydney; Jeremy McAnulty, NSW
Department of Health; William Rawlinson, University of New South Wales and
SEALS Department, Prince of Wales Hospital, Sydney; and Evan Sergeant, NSW
Department of Agriculture.
  --------------------------------------------------
      After an apparently new virus in the family Paramyxoviridae was
      isolated from pigs in August 1997, an investigation was carried
      out to assess its risk for humans. More than 250 persons with
      potential exposure to infected pigs were tested serologically.
      Two piggery workers with intense occupational exposure had high
      convalescent-phase antibody titers to this new virus. In early
      June 1997, both workers had an influenzalike illness with rash;
      serologic testing showed no alternative cause. Strong evidence
      indicates that the two men became ill from this new virus, but
      the mode of transmission from pigs to humans remains unknown.
Zoonotic illnesses due to viruses in the family Paramyxoviridae (i.e.,
Newcastle disease virus [1] and equine morbillivirus [2]) have been
described. An apparently new virus in the family Paramyxoviridae, isolated
from pigs in a piggery near Sydney, Australia, is described by Philbey et
al. in this issue. We describe epidemiologic investigations to assess the
risk the virus poses for humans and detail two probable cases of human
disease.
Piggery A, from which the virus was isolated, is a large commercial piggery
with animals housed in four discrete production units. At approximately 6
weeks of age, some pigs are transported to piggeries B and C for growing to
slaughter weight. Animals from piggery A are also supplied to a university
and a hospital for research.
After the new virus was isolated, an assay for neutralizing antibodies that
allowed testing of sera from animals and humans was developed at the
Elizabeth Macarthur Agricultural Institute. All 33 workers at piggery A
were tested with this assay for antibodies to the new agent. Other workers
who had come into contact with potentially infectious pigs from piggery A
were also tested: abattoir workers (n = 142), workers at the grower
piggeries B and C (n = 5), researchers and animal handlers (n = 41),
veterinarians and pathology laboratory workers (n = 24), and others (n =
6). Sixty delinked sera from women receiving routine prenatal screening
were tested as controls and were seronegative for the agent. Two workers
were seropositive, with virus neutralizing antibody titers of 128 and 512.
These results were confirmed by repeat collection and testing. Both workers
received a detailed clinical review and extensive serologic testing, the
results of which are described below.
In early June 1997, Patient 1 had sudden onset of malaise and chills
followed by drenching sweats and fever. He was confined to bed with severe
headaches and myalgia for the next 10 days. He had no cough, vomiting, or
diarrhea. After the third day, he went to a locum physician, who prescribed
amoxicillin. A day later, he noted a spotty red rash. He went to his usual
physician, who noted tenderness in both hypochondria, lymphadenopathy, and
a rubelliform rash and diagnosed acute Epstein-Barr virus infection.
However, subsequent review of the patient's medical notes showed a positive
result for Epstein-Barr virus immunoglobulin G (IgG) in 1991. He returned
to work after 14 days' absence but tired easily. He reported a 10-kg weight
loss during his illness.
Results of a clinical examination 2 months after this illness were normal
except for mild tenderness in the right hypochondrium. Results of
urinalysis, full blood count, erythrocyte sedimentation rate, C-reactive
protein concentration, and blood chemistries were normal. An upper
abdominal ultrasound indicated that liver size was at the upper limits of
normal, and the spleen was enlarged (15 cm long).
The worker had frequent prolonged contact with birthing pigs. He reported
that splashes of amniotic fluid and blood to the face were not uncommon and
that he often received minor wounds to his hands and forearms. His partner
tested negative for neutralizing antibodies to this agent.
Six other workers at the piggery reported an influenzalike illness during
the winter months, yet records showed that only two had more than 1 day off
work, the most being 4 days.
Patient 2 worked at piggery B. He also had onset of illness in early June
1997 characterized by fever, chills, rigors, drenching sweats, marked
malaise, back pain, severe frontal headache, and photophobia. He had no
cough, vomiting, or diarrhea. The headache resolved after 4 to 5 days. Four
days after onset of the illness, he noted on the torso a spotty, red,
nonpruritic rash, which lasted 7 days. He had largely recovered after 10
days, noting a 3-kg weight loss. No investigations were performed.
Results of a clinical examination 2 months after his illness were
essentially normal. Results of urinalysis, full blood count, erythrocyte
sedimentation rate, and C-reactive protein were within normal limits. Blood
chemistry results were normal except for mildly elevated liver function. He
was hepatitis Cantibody positive and IgA-deficient. An upper abdominal
ultrasound showed mild hepatomegaly with normal texture. The spleen was at
the upper limit of normal size.
This worker did not have contact with birthing pigs; however, he performed
autopsies on pigs without wearing gloves or protective eye wear. As with
Patient 1, exposure to pig secretions (e.g., feces, urine) was common. The
worker had received a delivery of young pigs from piggery A the week before
his illness.
Both workers had a similar illness in early June 1997. Both had high
convalescent-phase neutralizing antibody titers to this new virus.
Serologic testing of all 33 workers at piggery A for other human
paramyxoviruses excluded cross-reactivity as a cause for this finding.
Extensive serologic testing of both patients in September 1997 (Table) did
not identify an alternative cause for the illnesses.
The unexplained splenomegaly in the first worker may be an incidental
finding. The second worker had evidence of hepatitis C virus infection,
abnormal liver function tests, hepatomegaly, and IgA deficiency. None of
these findings need be implicated in the patient's presumed infection with
this paramyxovirus.
While single high antibody titers must be interpreted with caution, the
timing of the described illnesses in relation to the disease in pigs, the
similarity of the two cases, the exclusion of cross-reactivity due to
preexisting antibody to other paramyxoviruses, and the absence of serologic
results suggesting another cause constitute strong evidence that the
illness in these two men was caused by this new virus.
Although respiratory transmission is proposed as a mode of spread in pigs,
the mode of transmission from pigs to humans is unknown. If spread to
humans is by the respiratory route, infectivity appears much lower than in
pig-to-pig transmission. Alternatively, a different transmission mode such
as parenteral or permucosal exposure may be involved. Philbey et al. in
this issue present evidence suggesting that bats may be involved in the
ecology of this new virus. Neither of the two patients had contact with
bats.
   Table. Results of case investigations
  ------------------------------------------------------------------
                                                     Titer
                                         ---------------------------
   Serologic test(sup a)                 Patient 1       Patient 2
  ------------------------------------------------------------------
   Neutralizing antibody to new agent   128             512
   Antibody to equine morbillivirus      negative        negative
   CMV IgG                               positive        positive
   CMV IgM                               negative        negative
   EBV-VCA IgG                           positive        positive
   EBV-VCA IgM                           negative        negative
   EBV-EBNA IgG                          negative        positive
   Rubella IgG                           positive        positive
   Rubella IgM                           negative        negative
   Mycoplasma (CFT)                      < 4(sup b)      4(sup b)      
   Mycoplasma IgM                        negative        negative
   Adenovirus (CFT)                      8(sup b)	   8(sup b)
   Enterovirus (CFT)                     8(sup b)	   8(sup b)
   Influenza A (CFT)                     32(sup b)       16(sup b)
   Influenza B (CFT)                     8(sup b)        <4 (negative)
   Leptospiral agglutinins               negative        negative
   Brucella antibodies                   negative        negative
   Toxoplasma IgG                        positive        positive
   Toxoplasma IgM                        negative        negative
   Q Fever (phase 2 - CFT)               negative        negative
   Measles IgG                           positive        positive
   Measles IgM                           negative        negative
   Mumps IgG                             positive        positive
   Mumps IgM                             negative        negative
   RSV (CFT)                             < 8(sup b)      anticomple-
                                                         mentary
   Parainfluenza 1 (CFT)                 32(sup b)       < 16(sup b)
   Parainfluenza 2 (CFT)                 16(sup b)       < 16(sup b)
   Parainfluenza 3 (CFT)                 < 8(sup b)      < 16(sup b)
   HBsAg                                 negative        negative
   anti-HBc                              negative        negative
   anti-HCV                              negative        positive(sup c)
   anti-HIV (Western Blot)               negative        negative
   anti-HIV (EIA)                        negative        negative
  -------------------------------------------------------------------
   (sup a)CMV, cytomegalovirus; IgG, immunoglobulin G; EBV, Epstein-Barr
   virus; VCA, viral capsid antigen; EBNA, Epstein-Barr nuclear antigen;
   CFT, complement fixation test; RSV, respiratory syncytial virus;
   HBsAg, hepatitis B surface antigen; HBc, hepatitis B core; HCV,
   hepatitis C virus; EIA, enzyme immunoassay.
   (sup b)Not significant.
   (sup c)By two screening enzyme immunoassays.
Human infection with this new virus seems confined to those with intense
occupational exposure to recently infected pigs. Sentinel pig surveillance
indicates that the virus continues to circulate at piggery A. Ongoing
surveillance for influenzalike illnesses and a serologic testing program
have been instituted for the workers. In January 1998, 19 of 21 previously
seronegative workers had repeat testing; all remained negative. The
occupational health and safety body of the state, in conjunction with
agricultural and health authorities, has issued appropriate safety
guidelines for the industry.
Acknowledgments
We thank the Microbiology Department, Prince of Wales Hospital; CIDMLS,
ICPMR, Westmead Hospital; Dan Russell, Mid Western NSW Public Health Unit;
Paul Van Buynder, Southern NSW Public Health Unit; and staff of South
Western Sydney Public Health Unit.
Dr. Kerry Chant is director and medical officer of health, South Western
Sydney Public Health Unit, and conjoint lecturer, University of New South
Wales. Dr. Chant is responsible for infectious disease surveillance,
prevention and control, health-related environmental health issues, and
food safety in southwestern Sydney. Her research interests include
infectious disease and infection control issues in particular related to
blood-borne viruses and childhood immunization.
Address for correspondence: Peter Kirkland, Virology Laboratory, Elizabeth
Macarthur Agricultural Institute, Menangle, NSW Australia; fax:
61-2-4640-6429; e-mail: kirklap@agric.nsw.gov.au.
References
  1. Trott DG, Pilsworth R. Outbreaks of conjunctivitis due to the
     Newcastle disease virus among workers in chicken-broiler factories.
     BMJ 1965;5477:1514-7.
  2. O'Sullivan JB, Allworth AM, Paterson DL, Snow TM, Boots R, Gleeson LJ,
     et al. Fatal encephalitis due to novel paramyxovirus transmitted from
     horses. Lancet 1997;349:93-5.
Emerging Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA
URL: http://www.cdc.gov/ncidod/EID/vol4no2/chant.htm
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