A nearly monthlong halt in the production of two drugs that treat rare genetic disorders has not yet caused significant hardship for those who depend on the treatments, according to patients and advocates. 'We haven't heard any real upset in the patient community thus far,' said Jack Johnson, a Missouri man who takes Fabrazyme, one of the drugs made by Cambridge biotechnology company Genzyme Corp., and who also runs a support and information group for people with his disorder. Genzyme shut down its Allston production plant last month after it found a virus had contaminated a piece of equipment used to make the drugs. Although the virus is not believed harmful to humans, Genzyme decided to undertake a massive decontamination effort as a precaution. The plant manufactures Cerezyme, a drug for Gaucher disease, and Fabrazyme, which treats Fabry disease. Both are genetic enzyme disorders that allow wastes to build up in the body, swelling organs and causing other problems. The drugs each cost about $200,000 per patient annually. Geoff McDonough, head of Genzyme's genetic disease business unit, said the cleanup is on schedule and production is expected to resume by the end of the month. 'We'll be done with the cleaning portion of this by the end of the weekend,' McDonough said Thursday. 'That's a good feeling. We're right where we want to be.' Because of the shutdown, Cerezyme and Fabrazyme are in short supply - the company only had a few months' worth of inventory on hand when the virus was found. As a result, doses of the drugs - which are usually taken every two weeks - are temporarily being rationed among some of the 8,000 patients worldwide who use them. The rationing should end in September, McDonough said. After news of the expected shortage, Genzyme established a 'supply update' website for patients. In addition, doctors, patient advocates, and the company worked to set recommendations for how Fabry and Gaucher patients and their physicians should handle any rationing. It was decided that patients with less severe forms of the diseases or those who have been taking the drugs for a long time should skip up to two doses or take reduced amounts, while patients such as children and pregnant women should continue receiving regular treatments. Kevin R. Kline, who takes Cerezyme, said that so far he has not missed a dose because of the shortage. 'I'm at least in a position where I could postpone an infusion or ((take the drug)) monthly for a short term if need be,' Kline said. The New Jersey man has taken Cerezyme every two weeks for years, which means his body has been purged of the dangerous levels of waste fluids. At Massachusetts General Hospital in Boston, Dr. Katherine Sims, who does clinical work with Gaucher and Fabry diseases, said Genzyme has done a good job of communicating with physicians and patients about the supply disruption. 'Bottom line is that patient((s)) are doing well with the circumstances,' Sims wrote in an e-mail to the Globe. Meanwhile, Genzyme's McDonough described the cleanup as a 'cosmic plumbing job' that involves dismantling equipment Genzyme uses to make Cerezyme and Fabrazyme. Once the decontamination is completed, the equipment has to be reassembled, McDonough said. After that, the equipment will be restarted and tested, and only then will Genzyme begin growing small batches of genetically modified Chinese hamster ovary cells used to make the drugs. 'The whole situation, in general, has highlighted just how complex this manufacturing process is,' McDonough said. Erin Ailworth can be reached at eailworth@globe.com. 