The United Nations is struggling with two contagions: bed bugs at its Manhattan headquarters and a Caribbean cholera outbreak that many Haitians blame on UN peacekeepers. The world body needs to clean up its act on both counts.
While fumigators can rid the UN's upholstery of bed bugs, Haiti's cholera scourge is more difficult to handle. It has already killed more than 1,100 people and left more than 18,000 others in hospital.
The problem for the UN is that many Haitians say cholera was brought to the country by a unit of Nepalese peacekeepers, sparking days of violent protests in the country's north and now the capital, Port-au-Prince.
Angry Haitians point to a Nepalese peacekeeping base in Mirebalais, saying contaminated faeces leaked from septic tanks into a tributary and infected the Artibonite River, which runs through central Haiti and is used by locals for drinking and bathing.
Allegations gained credibility when the US Centers for Disease Control and Prevention (CDC) said the strain of cholera ravaging Haiti - perhaps the first outbreak the country has ever seen - matched those in South Asia, including Nepal.
The UN describes several tests on Nepalese soldiers, who number among the UN's 12,000-strong force in Haiti, saying all proved negative. The UN spokesman Farhan Haq said this week that the UN is still probing the origins of the outbreak, but that there is "no conclusive evidence" that the Nepalese were to blame.
But the UN spent several weeks downplaying the Nepalese involvement and stonewalling further tests. This fomented discontent and affirmed the fears of many Haitians. Dr Paul Farmer, an expert on poverty and medicine, said the UN's reluctance to delve into the outbreak was "politics ... not science".
This week's anti-UN riots in Port-au-Prince and Haiti's northern city, Cap-Haitian, which saw burning barricades, tear gas clouds and several deaths, show that the world body has - at the very least - failed to communicate with the people.
Haitians are still reeling from the January 12 earthquake, which claimed 300,000 lives. Many rioters number among the 1.3 million people still living in the squalor of makeshift camps. Few see any signs of the "wholesale national renewal" that UN secretary general, Ban Ki-moon, promised in March.
They are scared, vulnerable and looking for someone to blame - cynical of both their own government's capacity to rebuild a tattered nation and the chances of foreign donors coming good on pledges made in the weeks after the quake.
For these reasons, the UN should launch an independent probe into the origins of the cholera outbreak and make public its findings. If it does not, the cholera debate will overshadow more important issues to be decided when Haitians go to the polls on November 28.
Sadly, the bed-bug infestation at UN headquarters suggests that the world body cannot be counted upon when tackling contagious outbreaks - whether cholera in Haiti or brown bloodsuckers skulking in the furniture.
The UN has grappled with bed bugs since September last year, using detector dogs and fumigators to tackle an insect scourge that has now sunk its teeth into New York landmarks from the Empire State building to Carnegie Hall.
The resilient bugs have nevertheless spread across headquarters these past 14 months. This week, journalists formally accused the UN of taking a "piecemeal approach of treating only already infected areas" rather than a large-scale fumigation.
Thankfully, bed bug bites only cause welts and rashes. But, if the UN fails to grasp the nettle in Haiti and convince protestors that blue helmet troops did not introduce the choleric killer, the consequences will be much worse.