Explanation

Hantavirus Puumala IgG: what is measured?

Puumala virus is a hantavirus carried by the bank vole, and it causes most hantavirus infections in the Netherlands. People become infected by breathing in dust particles containing virus from droppings. This test measures IgG antibodies against the virus. IgG appears later than IgM, usually in the second week of illness, and after that probably remains detectable for life. As a result, IgG mainly shows that you have had the infection at some point.

What can it detect?

A past infection with Puumala virus, even if it caused no symptoms
Support for the diagnosis of nephropathia epidemica if the antibodies clearly rise between two blood samples

Result

What does the result mean?

Positive result

A positive IgG result means that your immune system has been in contact with Puumala virus. That may have been recently, but also years ago: about 90 in 100 infections with this virus cause no symptoms. In a national study, about 1.7 in 100 people in the Netherlands had these antibodies. A recent infection requires a clear rise between two blood samples, or a positive IgM result as well. Cross-reaction with another hantavirus is also possible.

Negative result

A negative IgG result makes a past Puumala virus infection unlikely. In the first days of illness it does not rule out an infection, because IgG only appears after IgM. If an infection that has only just started is suspected, IgM is the appropriate test, or a second blood sample after at least fourteen days to see whether the IgG antibodies rise.

After an abnormal result

If a recent infection is suspected, the doctor compares the result with a second blood sample after at least fourteen days and assesses kidney function; there is no specific medicine. Orthohantavirus infection is a notifiable disease in group C of the Dutch Public Health Act and must be reported to the GGD (municipal public health service) within one working day.

Reliability

How reliable is the test?

According to the LCI guideline (RIVM), serology is the appropriate method for diagnosing hantavirus infections; how often the test misses an infection or is falsely positive has not been well established. The main limitation is that the different hantaviruses react strongly to each other's tests, so a positive Puumala result does not prove that it was this particular virus. Because IgG probably remains for life, a single positive result says nothing about an active infection. In people without symptoms, the result is therefore mainly information about the past.

What can affect the result?

IgG probably remains detectable for life after a past infection and says nothing about an active infection.
There is extensive cross-reactivity with other hantaviruses; determining the type requires a neutralization test in a specialized laboratory.
In the first days of illness, IgG may still be negative while there is an infection.
Most infections with this virus cause no symptoms, so a positive result usually does not explain existing symptoms.

Who it is for

Who is the test useful for?

Useful for

Useful when a hantavirus infection is suspected, together with IgM and if needed a second blood sample, in people with sudden fever, headache, abdominal pain and reduced kidney function after contact with mouse droppings. Also useful to establish afterwards whether someone has had the infection, for example during source tracing. Not useful as a general check-up in people without symptoms; a positive result then usually means an old infection and does not change the management.

How common is it?

Orthohantavirus infection is rare in the Netherlands: between 2018 and 2023 an average of 31 cases per year were notified, ranging from 10 to 49. Almost all cases involve Puumala virus and come from the east and southeast of the country. In a national study in 2006 and 2007, about 1.7 in 100 people in the Netherlands had antibodies against Puumala virus; in Enschede this was 3.2 in 100.

The RIVM/LCI guideline on orthohantavirus infection

Drawbacks and risks

A positive result without matching symptoms usually points to an infection that passed unnoticed long ago, but can still lead to worry and unnecessary testing.
Due to cross-reaction with other hantaviruses, the result can wrongly suggest a Puumala virus infection.

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