![]() |
NSW Arbovirus Surveillance & Vector Monitoring Program | ![]() |
![]() ![]() |
For the season of 1998-99, the NSW Arbovirus Surveillance Program provided monitoring of mosquito vector populations and surveillance of arbovirus activity on the NSW western slopes and plains, coastal regions and metropolitan Sydney. The majority of sites operated between November and April.
The drought
conditions, which dominated the 1990's, were broken with heavy rainfall across much of the
state through winter and spring. This resulted in some extraordinary mosquito collections
from the inland, with Culex annulirostris numbers up to 34 times the
average. There was a high level of virus activity in the mosquitoes, with several Ross River (RR) isolates during November;
this has never occurred before during the history of the Program. All up there were a
record 104 isolates (4 RR, 68 SIN, 1 EH,
3 KUN, 1 KOK, 27 unknowns) from the inland. There were also
record numbers of notifications of human arbovirus infections during November, December
and January. These were concentrated in the Greater Murray Area Health region and were
mostly RR virus infections.
Mosquito
numbers on the north coast were below average during November to January. High localised
rainfall in mid summer resulted in several large collections in February and March, with
unusually high numbers of freshwater mosquitoes. Thirteen viruses (6 RR, 7 unknowns) were isolated from the
north coast. Record numbers of human notifications of Barmah Forest (BF) and RR were reported.
The south
coast had very dry conditions with mosquito numbers well below average. Three viruses (2
RR, 1 unknown) were isolated, all from Batemans Bay. There were a
number of notifications of RR and BF infections in humans.
Sydney
collections also yielded low mosquito numbers, however there were six isolates (2 RR, 4 STR), the majority from Aedes
notoscriptus. There were human RR
cases in rural Sydney and a RR
seroconversion in a horse prior to the human cases.
Overall,
1998-99 had the highest number of human notifications ever recorded for one season in NSW,
with 1,219 RR and 238 BF infections reported.
The major innovation for the current season was the introduction of the NSW Arbovirus Surveillance Web Site <http://www.arbovirus.health.nsw.gov.au/>. While the main function of the site is to rapidly disseminate surveillance results, a wide range of information on mosquitoes and arboviruses is included.