may be silent) with that virus. It usually, 
but not always, means that the current ap- 
parent illness is due to that virus. The 
results of virus isolation attempts must be 
correlated with the clinical, epidemiologic, 
and serologic data. 
b. Serologic Tests: 
Since it has been found that some individuals 
already have antibodies against certain 
viruses because of previous contact with 
that virus, the finding of antibodies in a 
single serum sample taken during or after a 
particular illness does not prove the etiology 
of that illness. However, a definite (4-fold 
or higher) rise in antibody titer from the 
acute stage of the disease to convalescence 
is usually significant. Although serologic 
tests yield indirect evidence of virus activity, 
they are more frequently informative than 
virus isolation attempts. An effort should be 
made in all cases to submit paired serum 
specimens in order to make a presumptive 
serologic diagnosis or to confirm the signifi- 
cance of the virus isolation by demonstrating 
a rise in antibody titer against the virus dur- 
the course of illness. 
Because of the large numbers of antigenic 
types, serologic studies on paired serum 
specimens usually cannot be performed in 
suspected enterovirus infections unless a 
virus is isolated from clinical material. When 
pericarditis or pleurodynia is present and 
adequate clinical information is provided, 
the microneutralization test for Coxsackie 
B viruses can be performed. 
In certain situations, a third serum specimen 
(taken late in convalescence, 2 or 3 months 
after onset) is extremely valuable. This is 
a recognized necessity in lymphocytic chori- 
omeningitis and most rickettsial diseases. In 
lymphocytic choriomeningitis, complement 
fixing antibodies may not occur until late in 
the course of the disease, approximately in 
the eighth week. In rickettsial diseases and 
in psittacosis and lymphogranuloma ven- 
ereum, the production of complement fixing 
antibodies may be suppressed or delayed in 
patients who are treated early with broad 
spectrum antibiotics. 
5. Packing and Shipment of the Specimens for 
Rabies Diagnosis 
After decapitation of the animal in the field, the 
head should be promptly cooled down and kept 
cold. Whenever possible, it should be delivered 
by messenger. If no messenger service is avail- 
able, the head should be packed for shipment 
by the fastest common carrier. It should be put 
into a suitable watertight metal container and 
tightly sealed. This container, in turn should 
be put into a larger watertight metal container. 
Cracked ice should be packed between the inner 
and outer container. The package should be 
clearly labelled and shipped to the laboratory 
with utmost dispatch. 
NOTE: Although freezing the specimen and 
shipping it frozen in dry ice (solid carbon di- 
oxide) or in nitrogen flasks will preserve the 
virus, quick microscopic examination may be 
delayed because of the time necessary for the 
head to thaw. Frozen portions of brain and 
salivary glands are easier to handle in the lab- 
oratory than are frozen entire heads. Immedi- 
ately upon thawing, the tissues should be pre- 
pared for direct microscopic examination for 
Negri bodies, for the fluorescent antibody test, 
or for the mouse inoculation test. 
33 
