新發現的tick-born virus infection

New
Tick-Borne Disease Found

Daniel
J. DeNoon

August
29, 2012 — A new virus, dubbed "Heartland virus," is being spread to
people by ticks common in the Southeast, the CDC reports.

The
only known cases are two northwestern Missouri men who fell ill in 2009. Ticks
had bitten both men, but they did not get better after treatment with
antibiotics. Tests later showed that the men did not have any tick-borne
bacterial diseases.

But
CDC researcher Laura K. McMullan, PhD, and colleagues did find something else:
a previously unknown virus in the patients' blood.

"This
virus could be a more common cause of human illness than is currently
recognized," they suggest in the New England Journal of Medicine.

The
two men, one age 57 and the other age 67, lived on different farms. The first
had only a single tick bite. The second said that over a two-week period he'd
received some 20 tick bites a day.

Both
men had fever, fatigue, diarrhea, and low levels of blood platelets and
white blood cells. The symptoms are similar to those of ehrlichiosis, a
relatively common tick-borne disease that is caused by bacteria.

The
first patient spent 10 days in the hospital. Two years later, he's still
feeling tired and often has headaches. At first he had memory problems and loss
of appetite, both of which slowly got better.

The
second patient was in the hospital for 12 days. Over the next four to six weeks
he had memory problems, fatigue, and loss of appetite. All of these symptoms
went away and did not come back over the next two years.

Questions
Remain

The
new virus is related to a tick-borne virus recently discovered in central and
northeastern China. That virus, called SFTSV, causes fever and loss of blood
platelets.

The
most common ticks in northwestern Missouri, where the two men were infected
with Heartland virus, are lone star ticks. These ticks
are found throughout the Southeast and up the Atlantic coast to Maine.

No
ticks carrying Heartland virus have been found. It's not clear whether a person
infected with the new virus can spread it to another person, or whether a tick
bite is necessary.

"Although
these two patients had severe disease, the incidence of infection with the
novel virus and range of disease severity are currently unknown," McMullan
and colleagues write.

They
warn health professionals to be on the lookout for people who fall ill after
getting tick bites and who do not get better after antibiotic treatment.

SOURCE:

McMullan,
L.K. The New England Journal of Medicine, Aug. 30, 2012.

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